To provide an electric wheel driving device capable of enhancing the durability of a wheel bearing, reducing the weight and the size of the device, and enhancing the disassemblability/assemblability.

The electric wheel driving device comprises an electric motor M to drive a planetary reduction gear 2 mounted on a wheel bearing 1, and a driving unit 4 having a rotary member 17. The wheel bearing 1 comprises a hub wheel 6 with an inner rolling surface 6a formed therein, an inner ring 7 pressed therein, an outer member 8 with double-row outer rolling surfaces 8a formed therein, and a rolling element 9. The planetary reduction gear 2 comprises a sun gear 3 provided on the rotary member 17, a plurality of planetary gears 12 arranged between the outer member 8 and the sun gear 3, and a carrier pin 14 to support these gears by a connection shaft 13. The driving unit 4 has the electric motor M separably arranged from the outer member 8 and the rotary member 17. The connection shaft 13 is connected to the hub wheel 6 via a serration, and the rotation of the electric motor M is transmitted to the hub wheel 6 via the rotary member 17 and the planetary reduction gear 2.