PURPOSE: To form a coupling device in a simple structure by hindering burying into a main body of a holding member by a first stopper and hindering projection from the main body of the fast holding member by a second stopper.

CONSTITUTION: A first stopper 40 corresponds in accordance with the external shape of a coin 300 and the prevention of the burying of a fast holding member 20 is released when the coin 300 is held to a holding section 21 for the fast holding member 20, and the fast holding of a key 30 is released when the fast holding member 20 is buried into a main body 10. Projection from the main body 10 is obstructed by the forward movement of a second stopper 50 energized in the progressive direction in the fast holding member 20 under the state. When the key 30 is inserted to the main body 10, the second stopper 50 is pushed by the front end section of the key 30 and retreated, and the obstruction of the projection of the fast holding member 20 is released. Since the fast holding member 20 is energized in the direction that the fast holding member 20 is protruded from the main body 10, the fast holding member 20 is projected instantaneously from the main body 10 to fast hold the key 30 while the holding section 21 is exposed. thus returning the coin 300.