diff --git a/README.ja.md b/README.ja.md
index 2327188..39c2492 100644
--- a/README.ja.md
+++ b/README.ja.md
@@ -72,6 +72,21 @@ Supervisor / Runner（policy, 親プロセス）
 
 ## インストール
 
+### ビルド済みバイナリ（推奨）
+
+最新リリースを `/usr/local/bin` にインストールします（`/usr/local/bin` が書き込めない場合は `~/.local/bin`）。
+
+```bash
+curl -fsSL https://raw.githubusercontent.com/reoring/roboppi/main/install.sh | bash
+roboppi --help
+```
+
+特定バージョンを入れる場合:
+
+```bash
+curl -fsSL https://raw.githubusercontent.com/reoring/roboppi/main/install.sh | bash -s -- --tag v0.1.0
+```
+
 前提:
 
 - Bun（CI は Bun 1.3.8）
diff --git a/README.md b/README.md
index ebe2d95..1769aea 100644
--- a/README.md
+++ b/README.md
@@ -76,6 +76,21 @@ Design docs:
 
 ## Install
 
+### Prebuilt binary (recommended)
+
+Install the latest release to `/usr/local/bin` (or `~/.local/bin` if `/usr/local/bin` is not writable):
+
+```bash
+curl -fsSL https://raw.githubusercontent.com/reoring/roboppi/main/install.sh | bash
+roboppi --help
+```
+
+Install a specific version:
+
+```bash
+curl -fsSL https://raw.githubusercontent.com/reoring/roboppi/main/install.sh | bash -s -- --tag v0.1.0
+```
+
 Prerequisites:
 
 - Bun (CI uses Bun 1.3.8)
diff --git a/install.sh b/install.sh
new file mode 100755
index 0000000..754d448
--- /dev/null
+++ b/install.sh
@@ -0,0 +1,246 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+REPO="reoring/roboppi"
+GITHUB="https://github.com/${REPO}"
+API="https://api.github.com/repos/${REPO}"
+
+log() {
+  printf '%s\n' "$*" >&2
+}
+
+die() {
+  log "roboppi install: $*"
+  exit 1
+}
+
+need_cmd() {
+  command -v "$1" >/dev/null 2>&1
+}
+
+usage() {
+  cat >&2 <<'EOF'
+Install Roboppi from GitHub Releases.
+
+USAGE
+  curl -fsSL https://raw.githubusercontent.com/reoring/roboppi/main/install.sh | bash
+
+OPTIONS
+  --tag <vX.Y.Z>          Install a specific release tag (default: latest)
+  --version <X.Y.Z>       Shorthand for --tag vX.Y.Z
+  --install-dir <dir>     Install directory for the roboppi binary
+  --prefix <dir>          Install to <dir>/bin
+  --no-verify             Skip sha256 verification
+  --dry-run               Print actions without installing
+  --help                  Show this help
+
+ENV
+  ROBOPPI_INSTALL_DIR     Same as --install-dir
+
+NOTES
+  - Supported: macOS (x64/arm64), Linux (x64/arm64)
+  - This script downloads the prebuilt binary from GitHub Releases.
+EOF
+}
+
+fetch() {
+  local url="$1"
+  if need_cmd curl; then
+    curl -fsSL "$url"
+    return 0
+  fi
+  if need_cmd wget; then
+    wget -qO- "$url"
+    return 0
+  fi
+  die "need curl or wget"
+}
+
+download_to() {
+  local url="$1"
+  local out="$2"
+  if need_cmd curl; then
+    curl -fSL "$url" -o "$out"
+    return 0
+  fi
+  if need_cmd wget; then
+    wget -qO "$out" "$url"
+    return 0
+  fi
+  die "need curl or wget"
+}
+
+sha256_file() {
+  local file="$1"
+  if need_cmd sha256sum; then
+    sha256sum "$file" | awk '{print $1}'
+    return 0
+  fi
+  if need_cmd shasum; then
+    shasum -a 256 "$file" | awk '{print $1}'
+    return 0
+  fi
+  die "need sha256sum or shasum"
+}
+
+resolve_latest_tag() {
+  # Extract "tag_name" from GitHub API JSON without jq.
+  fetch "${API}/releases/latest" |
+    awk -F'"' '/"tag_name"[[:space:]]*:/ {print $4; exit}'
+}
+
+map_platform() {
+  local os arch
+  os="$(uname -s 2>/dev/null || true)"
+  arch="$(uname -m 2>/dev/null || true)"
+
+  case "$os" in
+    Linux) os="linux" ;;
+    Darwin) os="macos" ;;
+    *) die "unsupported OS: ${os:-unknown}" ;;
+  esac
+
+  case "$arch" in
+    x86_64|amd64) arch="x64" ;;
+    arm64|aarch64) arch="arm64" ;;
+    *) die "unsupported architecture: ${arch:-unknown}" ;;
+  esac
+
+  printf '%s-%s' "$os" "$arch"
+}
+
+main() {
+  local tag=""
+  local install_dir="${ROBOPPI_INSTALL_DIR:-}"
+  local verify=1
+  local dry_run=0
+
+  while [[ $# -gt 0 ]]; do
+    case "$1" in
+      --tag)
+        [[ $# -ge 2 ]] || die "--tag requires a value"
+        tag="$2"
+        shift 2
+        ;;
+      --version)
+        [[ $# -ge 2 ]] || die "--version requires a value"
+        tag="$2"
+        if [[ "$tag" != v* ]]; then tag="v${tag}"; fi
+        shift 2
+        ;;
+      --install-dir)
+        [[ $# -ge 2 ]] || die "--install-dir requires a value"
+        install_dir="$2"
+        shift 2
+        ;;
+      --prefix)
+        [[ $# -ge 2 ]] || die "--prefix requires a value"
+        install_dir="$2/bin"
+        shift 2
+        ;;
+      --no-verify)
+        verify=0
+        shift
+        ;;
+      --dry-run)
+        dry_run=1
+        shift
+        ;;
+      --help|-h)
+        usage
+        exit 0
+        ;;
+      *)
+        die "unknown argument: $1 (try --help)"
+        ;;
+    esac
+  done
+
+  if [[ -z "$tag" ]]; then
+    tag="$(resolve_latest_tag || true)"
+    [[ -n "$tag" ]] || die "failed to resolve latest release tag; use --tag vX.Y.Z"
+  else
+    if [[ "$tag" != v* ]]; then tag="v${tag}"; fi
+  fi
+
+  local platform asset base_url
+  platform="$(map_platform)"
+  asset="roboppi-${tag}-${platform}.tar.gz"
+  base_url="${GITHUB}/releases/download/${tag}"
+
+  if [[ -z "$install_dir" ]]; then
+    if [[ -w "/usr/local/bin" ]]; then
+      install_dir="/usr/local/bin"
+    else
+      install_dir="${HOME}/.local/bin"
+    fi
+  fi
+
+  local tmp
+  tmp="$(mktemp -d 2>/dev/null || mktemp -d -t roboppi)"
+  trap 'rm -rf "$tmp"' EXIT
+
+  log "roboppi install: tag=${tag} platform=${platform}"
+  log "roboppi install: downloading ${asset}"
+
+  if [[ "$dry_run" -eq 1 ]]; then
+    log "dry-run: would download ${base_url}/${asset}"
+    log "dry-run: would install to ${install_dir}/roboppi"
+    return 0
+  fi
+
+  download_to "${base_url}/${asset}" "${tmp}/${asset}" || die "download failed: ${base_url}/${asset}"
+
+  if [[ "$verify" -eq 1 ]]; then
+    local sha_url sha_file expected got
+    sha_url="${base_url}/${asset}.sha256"
+    sha_file="${tmp}/${asset}.sha256"
+    download_to "$sha_url" "$sha_file" || die "download failed: ${sha_url}"
+    expected="$(awk 'NR==1 {print $1; exit}' "$sha_file")"
+    [[ -n "$expected" ]] || die "could not read expected sha256"
+    got="$(sha256_file "${tmp}/${asset}")"
+    if [[ "$got" != "$expected" ]]; then
+      die "sha256 mismatch for ${asset} (expected ${expected}, got ${got})"
+    fi
+  fi
+
+  mkdir -p "${tmp}/stage"
+  tar -xzf "${tmp}/${asset}" -C "${tmp}/stage"
+
+  local src_bin
+  src_bin="${tmp}/stage/roboppi"
+  [[ -f "$src_bin" ]] || die "archive did not contain roboppi binary"
+
+  if [[ -w "$install_dir" ]]; then
+    mkdir -p "$install_dir"
+    if need_cmd install; then
+      install -m 755 "$src_bin" "${install_dir}/roboppi"
+    else
+      cp "$src_bin" "${install_dir}/roboppi"
+      chmod 755 "${install_dir}/roboppi"
+    fi
+  else
+    if need_cmd sudo; then
+      sudo mkdir -p "$install_dir"
+      if need_cmd install; then
+        sudo install -m 755 "$src_bin" "${install_dir}/roboppi"
+      else
+        sudo cp "$src_bin" "${install_dir}/roboppi"
+        sudo chmod 755 "${install_dir}/roboppi"
+      fi
+    else
+      die "install dir not writable (${install_dir}); set --install-dir or install sudo"
+    fi
+  fi
+
+  log "roboppi install: installed to ${install_dir}/roboppi"
+
+  if command -v roboppi >/dev/null 2>&1; then
+    roboppi --version || true
+  elif [[ -x "${install_dir}/roboppi" ]]; then
+    "${install_dir}/roboppi" --version || true
+    log "roboppi install: ${install_dir} is not on PATH"
+  fi
+}
+
+main "$@"