To be friendly to a human body and environment, facilitate its assembling work, and reduce the cost by forming a compression spring member applying a snap action to a movable contact piece constituting a contact opening/ closing mechanism of phosphor bronze alloy or stainless steel treated by cold rolling.

A compression spring member 9 is composed of phosphor bronze alloy and a projection part 9c is formed in its base end part 9b side. The compression spring member is formed by bending a projection part 9d in the rear side of the trapezoidal top part so as to improve spring performance in mechanism and disperse a local compulsory stress energized by the spring member 9, thereby attaining the long life. Stainless steel treated by cold rolling can be also used as a material for the compression spring member 9. The compression spring member 9 is erected across a common fixing terminal piece 2 and a movable contact piece 8 so that the both ends 9a, 9b are detachable locked, and the both ends 10a, 10b of the receiver member 10 are erected across the common fixing terminal piece 2 and the movable contact piece 8 so as to be detachably locked.