A rack and pinion gear mechanism includes a rack forming member having a rack; a pinion gear which engages releasably with the rack of rack forming member; and an elastic member which contacts with one portion of the rack forming member and deformed by an elastic deformation corresponding to a displacement of the rack forming member by a confliction of tooth points, the one portion is located opposite side to a tooth of the rack that contacts firstly with a tooth of the pinion gear. The elastic member contacts with the one portion of rack forming member at just before and just after beginning of the engagement between the rack and the pinion gear, and the elastic member is apart from the rack forming member when the engagement is achieved. The rack and pinion gear mechanism further includes a positioning means to fix the elastic member in a cantilever manner to define a positioning of a free end of the elastic member in height. A tooth of the rack which firstly contacts with a tooth of the pinion gear at the engagement with the pinion gear, is made lower than the other teeth in its height of tooth top.