A work output device is revealed. The work output device includes two motor rotors respectively arrange at two ends of a horizontal main rotating shaft. An outer transmission shaft of each motor rotor starts rotating after the power is turned on. The rotating outer transmission shaft drives the main rotating shaft to rotate in one direction through a speed change gear mechanism. The motor rotors are synchronously driven to rotate around the main rotating shaft and move from a lower position to a higher position. At the moment, the power is turned off and the motor rotors turn back from the higher position to the lower position with the help of gravity. Thus a cycle of repetitive up-and-down half circle rotation is completed. Moreover, the main rotating shaft drives a work output shaft to rotate by a torque controller.