A prismatic secondary battery of one configuration has a current disconnection mechanism, and a distance from a first conductive member to a second conductive member along a surface of a first insulation member and passing an outer periphery of the first insulation member is greater than or equal to 2.4 mm. At least one of the first insulation member and a second insulation member is formed from a material having a weight reduction percentage of 100% in thermo gravimetric measurement under conditions of a measurement temperature of 25° C.-600° C., a temperature increase rate of 5° C.±0.5° C./min, a measurement atmosphere of inert gas flow, and an amount of measurement sample of 10 mg±5 mg.