An operating key part (60) includes hinge keys (11), protrusions (12), stoppers (13), a frame (20), and hinges (21), which are molded integrally out of thermoplastic resin. The frame (20) takes the form of a grid or lattice. Each of the hinge keys (11) is positioned in one box of the frame (20) and supported as floating through hinges (21) by the frame (20). The frame (20) has four protrusions (22) protruding from the corners of its front side. When the operating key part (60) is fitted to a main apparatus, the front ends of the frame protrusions (22) are positioned at a predetermined distance in a direction Y2 from the position to which the front sides of the hinge keys (11) have moved farthest in this direction.