This secondary battery is provided with: a battery element including a positive electrode, a negative electrode, and an electrolyte; an accommodation member for accommodating the battery element; anda safety valve mechanism attached to the accommodation member. The safety valve mechanism comprises: a valve member including an openable opening valve part; and an opening member including a plurality of opening parts and a plurality of protrusion parts, wherein the plurality of opening parts are radially disposed in a region facing the opening valve part with respect to the center of the regionas a base point, and the plurality of protrusion parts are radially disposed with respect to the center as a base point in a region outside the plurality of opening parts and protrude toward the plurality of opening parts. The number of the opening parts and the number of the protrusion parts are equal to each other, and each of the plurality of opening parts and each of the plurality of protrusion parts face each other in a center-facing direction.