An attachment structure is configured to attach a first member to a second member. The attachment structure includes a first engagement portion which is provided at one of the first member or the second member, and a second engagement portion which is provided at the other one of the first member or the second member and which engages with the first engagement portion at a predetermined attachment position to restrict a relative movement. One of the first member or the second member at which the second engagement portion is provided, is provided with spaces at both sides of the second engagement portion in the circumferential direction. The first member and the second member include a torque change portion which changes a torque such that the torque is larger at a preceding side and a succeeding side of the attachment position in the circumferential direction, than at the attachment position.