A brush holding apparatus is mounted to an inner wall surface of a rear bracket and a cap mounted to a head portion of a brush holder portion is exposed through an opening in the rear bracket. Brushes are housed inside brush insertion apertures of the brush holder portion and are placed in elastic contact with slip rings by springs. An abrasion detection terminal is insert molded into the brush holder portion, a contact thereof projecting inside one of the brush insertion apertures and coming into contact with the corresponding spring when the brushes are abraded by a predetermined amount.