Clamping members (12) are assembled to each side portion of a vehicle floor panel (11). Each clamping member (12) has a base portion (13). The base portion (13) has a wire harness holding portion (15), a sandwiched supporting piece (16), and a clip (24). The wire harness holding portion (15) receives a wire harness (14). The base portion (13) is assembled to the floor panel (11) by the clip (24). The sandwiched supporting piece (16) is formed such that its thickness decreases toward the distal end. The distal end of the sandwiched supporting piece (16) is held between an opening trim (29) and the floor panel (11).