PURPOSE: To attain curtailment of man-hours for an assembling operation and maintenance of accuracy related to the height position of a work by basically constituting the mechanism to load a plurality of assembling jigs on one base at voluntary height positions, and arranging a positioning means to set basic height positions in response to the respective assembling jigs on the other base.

CONSTITUTION: A plurality of bases 10, 12 are respectively constituted capably of being rotationally moved and indexed, and a plurality of assembling jigs 14 are uniformly loaded on one base 10. The assembling jig 14 sets and mounts automatically and accurately a supplied work W2 into the fitting hole of a work W1 to be assembled positioned and held on a base 16 fixed on the one base 10 at a decided height position. By the way, the assembling jig 14 elevatably moves a work holder 24 along the linear guide 20 of a base part 18 by means of an elevator device 22, and positions the lower end of the work holder 24 by means of a jig stopper. Meanwhile, the elevator device provided with a positioning means 38 is arranged on the other base 12 so as to be forced to face the assembling jig 14. Hereby, the height position relation of the supplied work W2 is maintained with its stable accuracy.