When the assembly is complete, the protrusion 2e of the leaf spring 2b abuts against the bottom wall surface 3g which is an inner bottom surface of the cover member 3 and the leaf spring 2b is bent. Since the protrusion is pushed against the cover member 3, the leaf spring 2b generates force of repulsion which pushes the frame member 2f toward the opposite direction of the cover member 3. In addition, since the leaf springs 2b are aligned straightly between three bosses 3b, the leaf spring 2b pushes the push button 2 toward the switch board 1 almost in parallel. In other words, if the push button 2 is held in the cover member 3, without further components, the push button 2 is pushed against the switch board 1 and there will not be a possibility of a wobble.