PURPOSE: To make possible to automatically incorporate a key and a coupling into a shaft by the intermediate fitting of the key to the shaft, the intermediate fitting of the coupling to the shaft equipped with the key obtained by said intermediate fitting, and by the complete fitting of the key and coupling to a rotary shaft.

CONSTITUTION: A key position detecting terminal 113 is provided into the key groove 112 of a hole into which the pump shaft 5 of a positioning block 110 vertically movable and provided with a pump shaft 5 driving part is inserted, and thereby the key groove position of the pump shaft 5 is defined. The key groove positioning block 110 is dropped into the key groove 112 of the key groove positioning block 110 while inserting a model shaft 105 into a hole into which the pump shaft 5 is inserted from the upper part and by applying a key 7 to be incorporated to the model shaft 105. Hereby, the key 7 is allowed to coincide with the key groove 112 end of the pump shaft 5. Further, by movably fitting a guide frame 104 to the model shaft 105 and by providing a key pushing bar 100, the key 7 is forced into the key goove 6 of the pump shaft 5. Accordingly, it is possible to incorporate the key 7 into the key groove 112 without particularly changing the shape of the end of the pump shaft.