A cancel cam structure which includes a cam section for allowing a ratchet to be put into contact therewith, is located radially outer to an axial direction of a steering shaft, and is pivotable along with pivoting of a steering wheel connected to the steering shaft; wherein: the cam section includes: an outer circumferential cam wall for allowing the ratchet to slide thereon; an inner wall located radially inner to the outer circumferential cam wall; and a coupling cam wall (13c, 13d) for coupling ends of the outer circumferential cam wall and the inner wall; the outer circumferential cam wall, the inner wall, and the coupling cam wall (13c, 13d) are formed parallel to the axial direction; and an enclosed space is formed by the outer circumferential cam wall, the inner wall, and the coupling cam wall (13c, 13d); and at least one of the outer circumferential cam wall and the inner wall has a projection section projecting toward the enclosed space; wherein the outer circumferential cam wall has an arc shape such that any cross-section thereof perpendicular to the axial direction is centered around an intersection of a central axis of the steering shaft and the cross-section, the arc shape having a certain diameter, and the outer circumferential cam wall extends uniformly in the axial direction; the inner wall has an arc shape such that any cross-section thereof perpendicular to the axial direction is centered around an intersection of the central axis and the cross-section, the arc shape having a certain diameter smaller than the diameter of the outer circumferential cam wall, and the inner wall extends uniformly in the axial direction; characterized in that the projection section is formed of a plurality of flat plate-like partition walls (140, 140a, 14b, 140c) standing upright in the axial direction, the partition walls dividing the enclosed space at prescribed intervals, and distances between the coupling cam wall (13c, 13d) and the partition wall (140a, 140c) adjacent thereto and between the partition walls adjacent thereto include at least two types of distances. the cam section includes: an outer circumferential cam wall for allowing the ratchet to slide thereon; an inner wall located radially inner to the outer circumferential cam wall; and a coupling cam wall (13c, 13d) for coupling ends of the outer circumferential cam wall and the inner wall; an outer circumferential cam wall for allowing the ratchet to slide thereon; an inner wall located radially inner to the outer circumferential cam wall; and a coupling cam wall (13c, 13d) for coupling ends of the outer circumferential cam wall and the inner wall; the outer circumferential cam wall, the inner wall, and the coupling cam wall (13c, 13d) are formed parallel to the axial direction; and an enclosed space is formed by the outer circumferential cam wall, the inner wall, and the coupling cam wall (13c, 13d); and at least one of the outer circumferential cam wall and the inner wall has a projection section projecting toward the enclosed space; wherein the outer circumferential cam wall has an arc shape such that any cross-section thereof perpendicular to the axial direction is centered around an intersection of a central axis of the steering shaft and the cross-section, the arc shape having a certain diameter, and the outer circumferential cam wall extends uniformly in the axial direction; the inner wall has an arc shape such that any cross-section thereof perpendicular to the axial direction is centered around an intersection of the central axis and the cross-section, the arc shape having a certain diameter smaller than the diameter of the outer circumferential cam wall, and the inner wall extends uniformly in the axial direction;