PURPOSE: To provide a method of assembling plural workpieces fixed by different methods, specially a clamped workpiece and a press-fitted workpiece disposed adjacently in parallel.

CONSTITUTION: Clamping mechanism 3 and press-fitting mechanism 6 are adjacently disposed in correspondence with the spaced positions of two workpieces. The workpiece 2 to be clamped is clamped first using the clamping mechanism 3, and in the state of maintaining the engagement of the clamped workpiece 2 with the clamping mechanism 3, the workpiece 1 to be press-fitted is press- fitted using the press-fitting mechanism 6. In the state of the pressing face of the press-fitting mechanism 6 being in contact with the press-fitted workpiece 1, the clamped workpiece 2 is clamped, and after performing preliminary press- fitting slowly utilizing the force of being energized in the press-fitting direction by clamping, the press-fitted workpiece 1 is press-fitted properly using the press- fitting mechanism 6.