A motor case (10) has connectors (30) fixed at motor case mounting holes (11), and an inverter case (50) has connectors (60) radially movable at inverter case mounting holes (65). The inverter case (50) is mounted on the motor case (10) so that the connectors (30, 60) fit together. A surface seal (45) is disposed on a lower surface of a flange (42) at an outer periphery of a housing (35) of the motor-side connectors (30), and is compressed elastically against an upper surface of the motor case (10) at an outer periphery of the motor case mounting holes (11). A metal pressing member (20) is fixed on the motor case (10) and presses the flange (42). An axial seal (47) is fit on the outer periphery of the housing (35) and is compressed elastically between the outer periphery and an inner periphery of the second mounting hole (65).