PROBLEM TO BE SOLVED: To prevent an operational error when releasing the lock in a slope device, etc.SOLUTION: An attachment device for a vehicle includes: a body side member 30 rotatably connected to a body of a vehicle a plate-like member 37 rotatably connected to the body side member 30 a main lock mechanism 40 for regulating the rotation of the body side member 30 with respect to the body at a storage position and an auxiliary lock mechanism 50 for regulating the rotation of the plate-like member 37 at a rotation reference position with respect to the body side member 30. The plate-like member 37 is provided with a regulation part 373t configured so as to prevent a lock release operation of the main lock mechanism 40 when the plate-like member 37 rotates from the rotation reference position.
