PURPOSE: To prevent the short-circuiting in an electric circuit due to erroneous operation by reforming an operating switch arranged with a plurality of push buttons in a ring shape, and eliminating apprehension of simultaneously pressing by mistake two or more of the push buttons.

CONSTITUTION: Push buttons 19a, 19b, 19c and a push button 19d, not shown in the drawing, are arranged in a ring shape. A seesaw plate 29 is arranged in the center surrounded by these push buttons. This seesaw plate 29 can be tilted by a center supporting point 32. When any one of the four push buttons is pressed down, the seesaw plate 29 is pressed to tilt by the pressed down push button, to impede pressing down the other three push buttons. Consequently, simultaneously operating a plurality of the push buttons is prevented.