A safety valve (40, 140, 240, 340) formed in a portion of a case of a sealed battery includes a fracture groove portion (50, 150, 250, 350) formed in a thin portion (42, 142, 242, 342). The thin portion (42, 142, 242, 342) is formed in a horizontally long shape or a vertically long shape that has a curved outer edge portion (45, 145, 245, 345) in which at least a portion of the outer edge portion (43) is curved. This thin portion (42, 142, 242, 342) has a center straight groove portion (60, 160, 260, 360) that extends in the longer direction of the thin portion in the center portion of the thin portion, and a pair of side groove portions (70, 170, 270, 370) that are formed in both side in the longer direction of the center straight groove portion (60, 160, 260, 360) and connected to longer direction end portions (60A, 60B, 160A, 160B, 260A, 260B) of the center straight groove portion. Here, a portion of the side groove portion (70, 170, 270, 370) is formed curved following the curved outer edge portion (45, 145, 245, 345).