A battery includes a bottomed cylindrical case body that accommodates an electrode body and a bottom-portion insulating plate (19) that is disposed between the electrode body and a bottom portion of the case body. The bottom portion of the case body has a gas discharge port that opens when an internal pressure of the battery reaches a predetermined pressure. The bottom-portion insulating plate (19) has a through hole. An aperture ratio, which is a ratio of an area of the through hole with respect to a total area of the insulating plate, is greater than or equal to 10% and less than or equal to 40%. A Young's modulus of the bottom-portion insulating plate at 25° C. is 10 GPa or greater.