PURPOSE: To attach a cover skin material to a base adhesively in a simple and efficient working manner and also prevent the cover skin material from becoming damaged during adhering process.

CONSTITUTION: A cover skin material 8 is retained in space using a plate 20 with a clamp 23 next, a base 2 is squeezed into the cover skin material 8 in an almost vertical direction and is bonded together with the latter. Further, the plate 20 is moved in an inner direction, and a base 2 is caused to ascend, so that the rear 4 of the base is caused to come in contact with the pressure part 26 of the plate 20 under pressure through the cover skin material 8 and the fold-back part of the cover skin material is allowed to stick to the base. A receiving mold is no longer required and need not be manufactured for each base without application of a pressure to the surface of the cover skin material. In addition, the terminal processing of the cover skin material can be done concurrently.