An electric generator incorporated into a hybrid vehicle including an engine and an electric drive motor and actuated by the engine, comprises a rotor mounted to one end portion of a crankshaft of the engine such that the rotor is rotatable integrally with the crankshaft; a cylindrical accommodating member surrounding an outer periphery of the rotor; and an air outlet provided on a peripheral wall portion of the accommodating member such that the air outlet opens in the vicinity of the outer periphery of the rotor and is tilted in a forward direction of a rotational direction of the rotor and in a radially outward direction.