A pressure valve to be arranged in a seal member sealing a casing in which a capacitor element is housed, the pressure valve having a base end positioned within the case and a tip positioned outside the case. The pressure valve includes a tapered portion having a tapered shape. At the top portion of the tapered portion, there is formed a slit able to undergo a state change between a close-state and an open-state by elastic deformation. When the casing internal pressure is less than a certain value, the slit maintains the close-state. When the casing internal pressure has reached the certain value, the slit undergoes a state change to the open-state, whereby the inside and outside of the case communicate with each other and the internal pressure is released from within the case.