This hinged cap (11) has: cap body (21) having a cylinder section (32) and a sealing ring (33) which is formed integrally with the cylinder section (32), extends downward from the cylinder section (32) with a gap provided between the sealing ring (33) and the inner peripheral surface of the cylinder section (32), and has a curved chamfered section (33d) formed on the inner peripheral surface of the lower end of the sealing ring (33), the cap body (21) being adapted to be mounted to a mouth (10a) formed at the upper end of a closed-end circular cylindrical container body (10)； a cover (22) having a top plate (41) which covers the cap body (21) and also having an annular ridge (43) which is provided to the top plate (41) and which is in close contact with the inner peripheral surface of the sealing ring (33)； and a hinge (23) formed integrally with the cap body (21) and the cover (22) and connecting the cap body (21) and the cover (22).鉸鏈式蓋(11)係具備蓋主體(21)、蓋部(22)及鉸鏈部(23)，蓋主體(21)係具有筒部(32)及密封環(33)且裝設在形成於有底圓筒狀的容器主體(10)的上端之口部(10a)，密封環(33)是與筒部(32)形成為一體，與筒部(32)之內周面隔著間隔而從筒部(32)往下方延伸且在下端部的內周面形成有曲面狀的倒角部(33d)；蓋部(22)係具有頂板部(41)及環狀突起(43)，頂板部(41)是覆蓋蓋主體(21)，環狀突起(43)是設置於頂板部(41)且與密封環(33)的內周面密合；鉸鏈部(23)是與蓋主體(21)及蓋部(22)形成為一體且用於連接蓋主體(21)和蓋部(22)。
