The present invention allows illumination light of a light source which leaks out to a light receiving element to be reliably shielded and allows components to be assembled to be unitized into a compact body. A light-shielding cylindrical section 31 and a light-shielding plate 32 interposed between a light-receiving side light guide 10 and a light emitting side light guide 11 are formed on a frame body 29 of a push button 2 as a single piece. Illumination light which leaks out from a light emitting element 6 and the light emitting side light guide 11 to a light receiving element 5 is shielded by the light-shielding cylindrical section 31 and the light-shielding plate 32. Support ribs 35 and a hook 41 for positioning a circuit substrate 7 are formed in the frame body 29, whereby the light guides 10, 11, light-shielding cylindrical section 31 and light-shielding plate 32 are unitized on the frame body 29.