An elastic wire which is linearly moved in an assembling direction parallel with an orthogonal surface perpendicular to an axial line of a steering shaft and thus assembled to a core member includes an attaching part that is attached to a core member and an engaging part that is engaged into a pin in a through-hole. The core member is provided with a surface restraint part that permits the attaching part to linearly move in the assembling direction and restrains the engaged attaching part from moving in a direction parallel with the orthogonal surface. The surface restraint part includes a restraining protrusion that permits the bent part 58 of the attaching part 56 to surmount the restraining protrusion as the elastic wire is linearly moved and restrains the bent part having surmounted the restraining protrusion from moving in an opposite direction to the assembling direction.