An air damper is provided. A piston member includes a stopper portion configured to come into contact with a cap in a state that a rod is pulled out to a maximum extent, and a deflection regulating portion configured to be positioned inside the engagement claw in the state to regulate an inward deflection of the engagement claw. An attachment portion rotatably attached to an attachment target portion is provided at an end portion of the rod. A contact surface is formed on the inner side of the engagement claw when viewed in an axial direction of the cylinder, the contact surface being capable of coming into contact with the deflection regulating portion when the rod swings in a direction of a rotation axis of the attachment portion with respect to the attachment target portion or in a direction intersecting the rotation axis.