PURPOSE: To facilitate the disassembly and assembly work by arranging the constitution such that the output shaft is born with bearing means on both sides of an AC servo motor and that the output shaft and a rotor and a bearing means fixed to the output shaft can be pulled out integrally from the side of a stator.

CONSTITUTION: In the first place, a cap 3 is removed from a housing 1 so as to expose the section of a detection means 39. Next, in that condition, sensors 45 and 47 are removed, and also a mounting nut 41 is removed from the output shaft 13. Thereby, a disc 43 is removed, and the detection means 39 is removed wholly. Next, four fixing bolts 23 fixing a bearing retaining means 21 to the housing 1 are removed. In that condition, as it is pulled out to the left in figure, the output shaft 13, bearings 25 and 27, a bearing press member 29, a bearing retaining means 21, a rotor 11, a washer 53, a fixing nut 51, and a bearing 35 are all pulled out from stator 9 side of an AC servo motor 7.