PURPOSE: To effectively cut OFF a circuit when a capacitor element insulator is damaged, to reduce in size a safety device and to decrease the size of a capacitor.

CONSTITUTION: Two or more cut pieces 2 having different lengths up to a bent part are so mounted on an insulating plate 8 as to be brought into contact with cutting blade 7 of an insulating plate 6 with a cutting blade, and mounted on the inner wall of a case body as a safety device in such a manner that the bent parts of the pieces 2 and the blade 7 are inclined.