To reduce the number of components and to eliminate need for increasing the depressing amount of a pressing button for actuating a release switch after a half-depressing switch is actuated by actuating the half-depressing switch when a first contact piece is brought into contact with a second contact piece and actuating the release switch when the second contact piece and a third contact piece are separated.

Normally, the contact piece 16 and the contact piece 17 are separated and the piece 17 and the contact piece 18 are in contact with each other. When the piece 16 is brought into contact with the piece 17, a half- depressing signal S1 becomes 'L' and half-depressing operation is executed. When the piece 17 is separated from the piece 18, a release signal S2 becomes 'H' and release operation is executed. After the release operation is executed, the piece 16 is separated from the piece 17. When the piece 17 is brought into contact with the piece 18, the signal S1 is returned to 'H' and the signal S2 is returned to 'L'. Thus, the half-depressing switch and the release switch which do not require the increase of the depressing amount of the pressing button are obtained.