Abstract: A cooling device for an electrical rotating machine is provided. The cooling device comprises; a yoke of an electric motor, end brackets and a rocker positioned in the outer circumferential portion of a commutator and fastened through the mediary of ventilation spaces to the inner circumference of one of the aforesaid end brackets. The cooling device further comprises; a screening plate for controlling the direction of cooling air being blown and a strength thereof, which is disposed between one end of the aforesaid rocker and the yoke; and a forcibly blowing device. With this cooling device, the cooling air is introduced through ventilating spaces defined radially inwardly of the aforesaid one end bracket into an electric motor by the forcibly blowing device, thereby forcibly cooling the surface of the commutator and the peripheral portion thereof.