Abstract: A device for direct-driving of wheels, adapted for various minivehicles, in particular, for bicycles, motorbikes, or motorcycles. The device comprises a fixed wheel axle, a wheel hub rotating about said wheel axle, an engine, and transmission units. Said engine and transmission units are enclosed inside the wheel hub; the engine's crankshaft is disposed offset from and parallel to the wheel axle; the transmission units have an overrunning clutch. The wheel hub is supported at both sides thereof. The transmission units can be completely disengaged from the wheel hub when the engine is stopped. A simple, safe and convenient conversion between the manpower-drive mode and the engine-drive mode is ensured on a vehicle equiped with the device.