A first cooling air passage is formed to let first cooling air generated by a cooling fan in from a radially outside of an inverter apparatus to cool a heat sink and out through exhaust holes provided on an outer peripheral side of a rear bracket by passing an inner periphery of the rear bracket. Also, a second cooling air passage is formed to let second cooling air generated by the cooling fan into a hollow portion of the inverter apparatus from an axially rear of a rotation shaft to cool a brush holder and a magnetic pole position detection sensor and out through the exhaust holes by passing the inner periphery of the rear bracket. Hence, cooling performance for the magnetic pole position detection sensor and the brush holder may be enhanced and an axial dimension may be reduced.