PURPOSE: To provide an AC generator for a vehicle in which the air of a low temperature is introduced by providing an air suction port at an end of a front side and invasion of water or mad can be suppressed.

CONSTITUTION: An air introduction passage 33 of a cooling air suction cylinder 31 is extended radially in an attitude tilted from a peripheral wall of a cover 3 adjacent to a pulley 4 toward a rotating direction of a drive shaft 9 from a centrifugal direction. An air suction port 32 of the cylinder 31 is disposed at a radial outside from a peripheral wall 1a of a front housing 1, and opened. Since flying direction of water, mad leaped up or scattered by a belt for driving the pulley 4 substantially coincides with an extending direction of the cylinder 31, the water on the mad are prevented from invading from the port into the cylinder 31.