A generator includes a housing; a rotational shaft at least partially inserted into the housing; a rotor coupled to the rotational shaft and rotated together when the rotational shaft is rotated; a stator positioned between an inner surface of the housing and an outer surface of the rotor; a cooling module including a fan cover coupled to the housing, and a fan installed inside of the fan cover to generate a flow of an air passing through an inside of the housing; and a rotation support part including a cylindrical bearing holder positioned inside of the housing, and a bearing which is coupled to an inner circumferential surface of the bearing holder and rotatably supports the rotational shaft, the bearing holder forming a flow path of the air blown by the fan in at least one of an inner side or an outer side.