A motor-assisted rotating wheel mechanism includes a rotating wheel, a rotating axle and an auxiliary motor. The rotating axle is rotationally disposed on a frame body and has two cranks with force-receiving members disposed at the two ends thereof, for allowing the force received by the force-receiving members to provide a rotational force to drive the rotating wheel to rotate and thus facilitate the auxiliary motor to output power, wherein the auxiliary motor is disposed between the two cranks disposed at the two ends of the rotating axle, and wherein the auxiliary motor includes a magnetic field having the same axle center as or parallel to the axle center, thereby facilitating the auxiliary motor to output power in cooperation with the rotating power provided by the rotating axle to synchronically drive the rotating wheel.