To provide an auxiliary power device which is attachable also to a small suitcase or shopping cart.

The device includes a carry base for fixing a suitcase 1; a device storage portion 9 and a storage portion for storing a battery pack 6, which are integrated to the carry base; a carry frame 2 fixed to both lateral ends of the storage portion for the battery pack 6; and a handle 8 with a built-in leaf switch. A pair of fixed legs 5a are fixed to both lateral ends on the bottom front side of the carry base, and a pair of wheels 4a, 4b are rotatably fixed to both lateral ends on the bottom rear side thereof. A drive wheel 10 is provided at an intermediate position between the wheels 4a, 4b. A wheel spur gear is attached to the drive wheel 10 in a stationary manner. A motor torque change-over switch 7 is attached to the rear surface of the device storage unit 9 so as to be freely operable from outside. A drive unit such as a geared motor is incorporated to the device storage unit. A detachable dry battery or rechargeable battery is stored in the battery pack.