The IC fixing component includes a locking case accommodating the IC in such a manner that a side of the IC out of a face-to-face contact with the heat dissipation plate is brought into a face-to-face contact with the locking case so as to be covered and a through hole and a rotation stop protrusion inserted into a rotation limiting hole. After the IC has been accommodated in the locking case, the screw member inserted through the through hole is screwed into a screw hole of the heat dissipation plate so that the side of the IC out of face-to-face contact with the locking case is pressed by the locking case thereby to be brought into a face-to-face contact with the heat dissipation plate.