A tip of a pair of arm portions that integrally extends from a fixed portion and both side portions of a front portion side of a key top are connected with each other in a coupling portion. When a downward pressing force is applied to a center of an operation surface of the key top, a bending moment using a connection portion of a substrate side as a fulcrum and a bending moment using the coupling portion of a tip side as a fulcrum act on the arm portion. The arm portion is deformed into a S-shape having bending deformation portions, and therefore the key top may be lowered in a nearly horizontal posture. The key top has a structure in which both side portions thereof are supported by the arm portions, thereby ensuring a small size and a large elevating stroke.