A mounting member to be mounted to an obverse side of a cover part arranged at a central portion of a steering wheel includes corner parts 31a, 31b, 31c, and 31d having hook parts 36-3, 36-4, 36-5, and 36-6 protruding from their reverse sides, the hook parts 36-3, 36-4, 36-5, and 36-6 being capable of interlocking with holes formed at the cover part. The hook parts 36-3, 36-4, 36-5, and 36-6 are arranged at narrow parts 37a and 37b between a contour 33 of the mounting member 30 and openings 35a and 35b formed along the contour 33.