Due to the meshing of the gears, the following force works on the rack. A separating force (Fα) determined by a pressure angle of gears, a lateral force (Fβ) determined by an angle of torsion of the rack, and drag (Fr) for offsetting angular moment occurring in the rack due to the lateral force (Fβ). A resultant (F) of the force works from the rack on the rack guide. When the line of this resultant (F) is held on the “inner side” of the end portions of the needle bearing 25 in this rolling type rack guide 21, the rotation of the roller 22 becomes stable.