Provided is an automotive alternator having structure for preventing entry and discharging of foreign matters irrespective of a posture of a brush unit, to thereby allow normalization of the brush unit. The brush unit of the automotive alternator includes a slip ring, a brush, a brush holder, and a slip ring cover coaxially spaced from the slip ring and having an inner peripheral surface surrounding substantially an entire periphery of the slip ring. The inner peripheral surface of the slip ring cover has a tapered surface increasing in diameter from a first end on the frame side toward a second end having a fully-open opening. The fully-open opening is sealed by a sealing member that forms a labyrinth seal with the second end.