bearing hole 14 e also the motor shaft support bearing 31 is disposed between an inner diameter surface of the boss 38 a and the speed reducer input shaft 30 the carrier support bearing 43 positions the speed reducer side carrier 38 with respect to the casing 14 also the motor shaft support bearing 31 positions the motor shaft 21 with respect to the casing 14 via the carrier support bearing 43 the speed reducer side carrier 38 has an outer circumferential edge which has a plurality of connection tabs 40 see fig1 and fig3 each bent toward the differential device 13 at a space along its circumferential direction these connection tabs 40 are inserted into the ring gear disc region 44 a of the differential side ring gear 44 to fasten the speed reducer side carrier 38 and the differential side ring gear 44 with each other as shown in fig1 fig2 and fig6 the differential device 13 is constituted by the differential side ring gear 44 a differential side sun gear 45 which is radially inside thereof and is coaxially therewith double pinion differential side pinion gears 46 a 46 b engaged with each other and disposed between the ring gear 44 and the sun gear 45 differential side pinion shafts 47 47 b which support these pinion gears 46 a 46 b and a differential side.