To provide a rack and pinion provided with a rack and a large gear actively engaged with each other.

A motion of a rack 20 causes a rotation of a large gear 30 and in contrast thereto, the rotation of the large gear 30 moves the rack 20. A side fitting is provided in a 'buried' space being not a space, i.e., in a shape of a tableland (end area) 26 at the back of the outermost space between teeth 21 at the tooth line edge of the rack 20 and thereby, it is prevented that a tooth 31b of the large gear 30 is engaged therewith. A motion of the large gear 30 against the rack 20 is possible in a lateral direction, i.e., a longitudinal direction of the rack 20 by a bearing 11 of the large gear 30. The large gear 30 is pushed out from the bearing 11 by the motion exceeding the side fitting. Thereby, a mechanism is protected against an overload.