{
  "spec_version": "3",
  "endpoint": "timeline",
  "stock_code": "9002",
  "company_name": "西武鉄道",
  "content_lang": "ja",
  "meta_lang": "en",
  "canonical_url": "https://the-shashi.com/tse/9002/",
  "api_url": "/api/9002/timeline.json",
  "updated": "2026-08-18",
  "license": "© 2026 Yutaka Sugiura. All rights reserved.",
  "attribution": "The社史 (the-shashi.com) — https://the-shashi.com/tse/9002/",
  "source": {
    "primary": [
      "有価証券報告書",
      "https://keibatsugaku.com/seibu_tetsudo/",
      "https://www.seibuholdings.co.jp/group/history/"
    ],
    "extraction": "有価証券報告書の沿革を基礎に、社史・報道で補完",
    "row_field": "source"
  },
  "timeline": [
    {
      "date": "1912/5",
      "importance": 1,
      "event": "武蔵野鉄道設立（資本金100万円）",
      "source": "有価証券報告書"
    },
    {
      "date": "1915/4",
      "importance": 2,
      "event": "池袋〜飯能間（現・池袋線）営業開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1929/9",
      "importance": 1,
      "event": "飯能〜吾野間（現・池袋線）営業開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1940/3",
      "importance": 1,
      "event": "多摩湖鉄道（現・多摩湖線）を合併",
      "source": "有価証券報告書"
    },
    {
      "date": "1940/12",
      "importance": 2,
      "event": "堤康次郎氏が武蔵野鉄道社長に就任",
      "source": "https://www.seibuholdings.co.jp/group/history/"
    },
    {
      "date": "1945/9",
      "importance": 3,
      "event": "旧西武鉄道（現・新宿線）を合併し商号を西武農業鉄道に変更",
      "source": "有価証券報告書"
    },
    {
      "date": "1946/11",
      "importance": 2,
      "event": "商号を西武鉄道に変更",
      "source": "有価証券報告書"
    },
    {
      "date": "1949/5",
      "importance": 1,
      "event": "東京証券取引所に上場",
      "source": "有価証券報告書"
    },
    {
      "date": "1950/1",
      "importance": 1,
      "event": "西武園遊園地が開業",
      "source": "有価証券報告書"
    },
    {
      "date": "1952/3",
      "importance": 2,
      "event": "新宿線高田馬場〜西武新宿間営業開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1954/1",
      "importance": 2,
      "event": "小島正治郎氏が社長に就任",
      "source": "https://keibatsugaku.com/seibu_tetsudo/"
    },
    {
      "date": "1955/10",
      "importance": 1,
      "event": "赤坂プリンスホテルが開業",
      "source": "有価証券報告書"
    },
    {
      "date": "1956/1",
      "importance": 2,
      "event": "ホテル事業を分離しプリンスホテルを設立",
      "source": "https://www.seibuholdings.co.jp/group/history/"
    },
    {
      "date": "1959/4",
      "importance": 1,
      "event": "子会社の池袋通運が商号を西武運輸に変更",
      "source": "有価証券報告書"
    },
    {
      "date": "1964/8",
      "importance": 1,
      "event": "東京プリンスホテルが開業",
      "source": "有価証券報告書"
    },
    {
      "date": "1964/10",
      "importance": 1,
      "event": "西武園ゴルフ場が開業",
      "source": "有価証券報告書"
    },
    {
      "date": "1968/5",
      "importance": 1,
      "event": "拝島線玉川上水〜拝島間営業開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1969/4",
      "importance": 1,
      "event": "子会社の西武自動車が商号を西武バスに変更",
      "source": "有価証券報告書"
    },
    {
      "date": "1969/10",
      "importance": 3,
      "event": "西武秩父線吾野〜西武秩父間営業開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1973/11",
      "importance": 2,
      "event": "堤義明氏が社長に就任",
      "source": "https://keibatsugaku.com/seibu_tetsudo/"
    },
    {
      "date": "1974/2",
      "importance": 1,
      "event": "西武ゴルフ開発（現・西武ゴルフ）を設立",
      "source": "有価証券報告書"
    },
    {
      "date": "1976/11",
      "importance": 1,
      "event": "八王子ニュータウン西武北野台分譲地を分譲開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1978/1",
      "importance": 2,
      "event": "福岡野球を買収し西武ライオンズが発足",
      "source": "https://www.seibuholdings.co.jp/group/history/"
    },
    {
      "date": "1978/7",
      "importance": 1,
      "event": "品川プリンスホテルが開業",
      "source": "有価証券報告書"
    },
    {
      "date": "1979/4",
      "importance": 1,
      "event": "西武球場が完成",
      "source": "有価証券報告書"
    },
    {
      "date": "1983/10",
      "importance": 1,
      "event": "西武有楽町線新桜台〜小竹向原間営業開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1985/4",
      "importance": 1,
      "event": "山口線新交通システム営業開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1989/1",
      "importance": 2,
      "event": "仁杉巌氏が社長に就任",
      "source": "https://keibatsugaku.com/seibu_tetsudo/"
    },
    {
      "date": "1994/12",
      "importance": 1,
      "event": "西武有楽町線練馬〜新桜台間営業開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1996/6",
      "importance": 2,
      "event": "戸田博之氏が社長に就任",
      "source": "https://keibatsugaku.com/seibu_tetsudo/"
    },
    {
      "date": "2000/6",
      "importance": 1,
      "event": "武蔵丘車両検修場を開設",
      "source": "有価証券報告書"
    },
    {
      "date": "2003/3",
      "importance": 2,
      "event": "池袋線桜台〜練馬高野台間の高架複々線化工事が完成",
      "source": "有価証券報告書"
    },
    {
      "date": "2004/3",
      "importance": 3,
      "event": "有価証券報告書における株主構成の虚偽記載が発覚",
      "source": "https://www.seibuholdings.co.jp/group/history/"
    },
    {
      "date": "2004/4",
      "importance": 2,
      "event": "総会屋への利益供与事件を受け社長交代",
      "source": "https://keibatsugaku.com/seibu_tetsudo/"
    },
    {
      "date": "2004/12",
      "importance": 3,
      "event": "西武鉄道株式の上場廃止",
      "source": "有価証券報告書"
    },
    {
      "date": "2005/5",
      "importance": 2,
      "event": "後藤高志氏が社長に就任",
      "source": "有価証券報告書"
    },
    {
      "date": "2006/2",
      "importance": 3,
      "event": "株式移転により持株会社の西武ホールディングスが発足し西武鉄道はその完全子会社に",
      "source": "有価証券報告書"
    },
    {
      "date": "2006/3",
      "importance": 1,
      "event": "一連のグループ再編手続きが完了",
      "source": "有価証券報告書"
    }
  ]
}