A flange 62 having motor mounting through holes 63 is provided on a motor 6, motor mounting holes 19 are provided on a base body 1, so that motor mounting screw 61 are passed through the motor mounting through hole 63 from a back surface 1b side so as to be screwed into the motor mounting holes 19 to fix the motor 6 to the base body 1. Housing mounting holes 83 are provided on a control housing 8, housing mounting through holes 17 are formed on the base body 1 so as to be offset from portions which are in abutment with the flange 62, so that housing mounting screws 81 are passed through the housing mounting through holes 17 from the back surface 1b side so as to be screwed into the housing mounting holes 83 to fix the control housing 8 to the base body 1.