A rack-and-pinion steering system comprising: a pinion shaft having pinion teeth; and a rack shaft on which rack teeth are formed which mesh with the pinion teeth, wherein an outer circumferential surface of the rack shaft includes a first area which is a concave formed on an outer circumferential surface of the rack shaft and extending in the axial direction and a second area which is an area of the outer circumferential surface excluding the first area and lies adjacent to an end portion of the first area in the axial direction, the rack teeth are formed in the first area, and a chamfered portion is provided on a boundary between the end portion of the first area and the second area to chamfer a corner portion on the boundary, characterized in that the rack-and-pinion steering system comprises a rack bush which supports the rack shaft so that the rack shaft slides in an axial direction of the rack shaft, and the rack bush includes a teeth side support portion configured to bring into contact with the second area so as to support the rack shaft from a side where the rack teeth are formed, wherein an end face of the rack shaft is formed at the end portion and intersects a flat surface formed on the first area as a bottom surface, at almost right angles so as to be inclined at a slight inclined or tilt angle (α), such as about 15°, with respect to a normal direction to the flat surface, the chamfered portion is an inclined surface which is inclined at a slight inclined or tilt angle (β) with respect to an imaginary line which extends along the outer circumferential surface of the second area in the axial direction and is provided to extend between the outer circumferential surface of the second area and the end face of the first area, and when seen in a direction which is at right angles to the axial direction, the chamfered portion is formed into a semicircular shape which expands in a direction in which it moves away from the first area. a pinion shaft having pinion teeth; and a rack shaft on which rack teeth are formed which mesh with the pinion teeth, wherein an outer circumferential surface of the rack shaft includes a first area which is a concave formed on an outer circumferential surface of the rack shaft and extending in the axial direction and a second area which is an area of the outer circumferential surface excluding the first area and lies adjacent to an end portion of the first area in the axial direction, the rack teeth are formed in the first area, and a chamfered portion is provided on a boundary between the end portion of the first area and the second area to chamfer a corner portion on the boundary, characterized in that the rack-and-pinion steering system comprises a rack bush which supports the rack shaft so that the rack shaft slides in an axial direction of the rack shaft, and the rack bush includes a teeth side support portion configured to bring into contact with the second area so as to support the rack shaft from a side where the rack teeth are formed, wherein an end face of the rack shaft is formed at the end portion and intersects a flat surface formed on the first area as a bottom surface, at almost right angles so as to be inclined at a slight inclined or tilt angle (α), such as about 15°, with respect to a normal direction to the flat surface, the chamfered portion is an inclined surface which is inclined at a slight inclined or tilt angle (β) with respect to an imaginary line which extends along the outer circumferential surface of the second area in the axial direction and is provided to extend between the outer circumferential surface of the second area and the end face of the first area, and when seen in a direction which is at right angles to the axial direction, the chamfered portion is formed into a semicircular shape which expands in a direction in which it moves away from the first area.