Safety device for sealed battery and sealed battery using it

The present invention relates to a safety device to make a closed battery explosion-proof and a closed battery with the safety device. A safety device for a closed battery capable positively preventing a rupture due to a rapid internal pressure rise at over-packing and short-circuiting and being produced inexpensively, a positive electrode lid () attached to one end of an outer covering can () comprises a pressure receiving plate () forming the innermost lid and connected to positive electrode () of an electrode unit () via positive electrode lead (), a shielding plate () forming a middle lid and electrically connected to the pressure receiving plate () via a center contact (), and a sealing plate () forming the outermost lid and electrically connected to the shielding plate (). The center contact () is formed of a projection () having a first flat contact surface () of the pressure receiving plate () and a second flat contact surface () of the shielding plate (), and a plurality of annular grooves () are alternately provided around the second flat contact surface () so as to face each other at 180° intervals, the annular grooves () being covered with a metal foil () to form valve membranes ().