A damper includes a cylinder, a rod including a first engaging portion at a tip end thereof, and a piston formed of an elastic resin material. The piston includes a convex portion provided so as to protrude at a base end portion located on a rod base end side and always in pressure contact with an inner circumference of the cylinder. During damper braking, the first engaging portion of the rod abuts against the other end portion of the piston, and an axial compression force acts on the piston between the first engaging portion and the convex portion in pressure contact with the inner circumference of the cylinder.