To provide a low-cost back door side stopper easy to assemble.

A first abutting part (corner part 53e) and a second abutting part (corner part 53f) which are separated in a radial direction of rotation of at least back door are formed in a projection part 53 of a male stopper member 51. An elastic body (cushion rubber 113) where the first abutting part (corner part 53e) and the second abutting part (corner part 53f) of the projection part 53 of the male stopper member 51 can be abutted is provided on an engaging part 103 of a female stopper member 101.