A rack shaft is supported at three positions including a gear housing receiving an engagement portion between a rack gear and a pinion near one end in an axial direction with respect to a rack housing corresponding to a support body thereof, a housing near the other end, and a hollow tube housing in an approximately center portion of the rack shaft. A bush made of a resin and constituted by a cylinder body is used for supporting the rack shaft by the hollow tube housing in the approximately center portion of the rack shaft. The bush is provided with a plurality of cut grooves extending in an axial direction thereof, and is provided with a curve forming portion substantially supporting the rack shaft and extending toward an inner side in a center portion in the axial direction thereof.