To provide an assembling device for a permanent magnet synchronous motor which can set the length of a space between a rotor and a stator accurately and which can assemble a motor efficiently.

An assembling device has such a structure that one end 4a of a rotor shaft 4 and an end 5a of a temporary shaft 5 connected to the other end of the rotor shaft are fixed by stator jigs 7a, 7b of shaft supports 7, 7 installed on a stand 6 to position a rotor 1 and guide pins 11 which are so positioned that the length of a space between a stator 8 and the rotor 1 may be a specified value are stuck in a guide frame 10 so located as to cover the rotor 1 and an outer surface of a stator frame 9. The stator 8 is moved by means of chain blocks 13, 13 installed on legs 9a of the stator frame 9 with a small space between the guide pins 11 and an outer wall face of the stator frame 9 being kept the same and then is inserted into the rotor 1.