What is provided is an attachment member that can be respectively attached to target members of different types, the member including a member main body, a first protrusion which is provided at an end portion of the member main body and is engageable with a first engaged part formed on a first target member, a second protrusion which is provided at the end portion of the member main body and is engageable with a second engaged part formed on a second target member, and an advancement and retraction mechanism which is configured to cause the second protrusion to advance and retract from the end portion of the member main body.