An expandable/contractable sheet (31) having a plurality of elastic members (35) positioned between a first sheet (32) and a second sheet (33) that are joined by a plurality of weld sections (50), and comprising: a first weld section row (61) that has a plurality of the weld sections (50) lined up neighboring one another in a vertical direction； and a second weld section row (62) that is positioned neighboring the first weld section row (61) to one side in a left/right direction, wherein the first weld section row (61) has a first protruding section (61P1) and a second protruding section (61P2) that protrude to the one side, the second weld section row (62) has a third protruding section (62P3) that protrudes to the other side in the left/right direction, and in a natural state, an other side end (62P3C) of the third protruding section (62P3) is located further to the other side than a straight line connecting a one side end (61P1A) of the first protruding section (61P1) and a one side end (61P2B) of the second protruding section (61P2).本發明之課題係在於提供不僅具有柔軟性，亦可在表面形成不規則的細微的皺紋之伸縮性薄片。 用以解決課題之手段為，一種伸縮性薄片，係在藉由複數個熔接部(50)接合之第1薄片(32)與第2薄片(33)之間，配置有複數個彈性構件(35)之伸縮性薄片(31)，其特徵為具備有：具有在上下方向相鄰排列之複數個熔接部(50)的第1熔接部列(61)、及相鄰配置於第1熔接部列(61)的左右方向之一方側的第2熔接部列(62)，第1熔接部列(61)係具有朝前述一方側形成為凸狀之第1凸部(61P1)與第2凸部(61P2)，第2熔接部列(62)係具有朝左右方向的另一方側形成為凸狀之第3凸部(62P3)，在自然狀態，前述第3凸部(62P3)的前述另一方側之端部(62P3C)是位於較將第1凸部(61P1)的前述一方側之端部(61P1A)和前記第2凸部(61P2)的前述一方側之端部(61P2B)連結的直線更靠近前述另一方側。
