Provided are: a multi-layer film for the outer packaging of a disposable heating pad that: has exceptional gas barrier properties for inhibiting the transmission of oxygen gas, water vapor, etc.； makes it possible to prevent expansion caused by hydrogen gas generated during periods of storage； and has exceptional seal strength, impact resistance, and weather resistance. Also provided is a disposable heating pad. In the outer packaging of a disposable heating pad, the outer packaging being formed from a multi-layer film including a first barrier layer (10) and a second barrier layer (20), the first barrier layer (10) and the second barrier layer (20) comprise a polyvinylidene chloride layer (12) or polyvinylidene chloride layer (22) formed by applying a polyvinylidene chloride coating to at least one surface (upper side in FIG. 1) of a heat-resistant resin substrate (11) or heat-resistant resin substrate (21).本發明提供一種阻止氧氣、水蒸氣等之透過之阻氣性優異，並且可防止由保存期間中所產生之氫氣引起之膨脹，且密封強度、耐衝擊性、耐候性優異的拋棄式發熱包外袋用多層膜及拋棄式發熱包。於由包含第1阻隔層10及第2阻隔層20之多層膜所形成之拋棄式發熱包外袋中，第1阻隔層10及第2阻隔層20包含在耐熱性樹脂基材11或耐熱性樹脂基材21之至少一個面(圖1中上側)塗佈聚偏二氯乙烯而成之聚偏二氯乙烯層12或聚偏二氯乙烯層22。
