To reduce wear in a bearing and a housing caused by thrust force produced in the motor shaft in a rotating electrical machine with a speed reducer using a helical gear speed reducer.

The rotating electrical machine includes: a stator 3; a rotor 4 attached to a helical gear comprising a speed reducing mechanism and rotatably provided on the stator 3 with a predetermined gap in-between; a first bearing that supports the shaft of the rotor 4 on the speed reducing mechanism side through a ball bearing 6a; and a second bearing that supports the shaft of the rotor 4 on the anti-speed reducing mechanism side in an enclosure through a grease-lubricated ball bearing 6b and has an insert material 18 between the grease-lubricated ball bearing 6b and the enclosure.