A seal type storage battery has a battery case which has a sealing assembly for sealing an opened portion of an outer case, which holds an electricity generating element. The sealing assembly includes a pressure-sensitive conductive rubber member in the battery case. The pressure-sensitive conductive rubber member has a resistance that changes continuously depending on a rise of inner pressure in the battery case. A lead connecting with the, pressure-sensitive conductive rubber extends outside of the battery case, and the lead is capable of outputting a pressure detecting signal to outside.