PURPOSE: To improve stability of a main body and load detecting accuracy by arranging a generating torque detecting means on the side where rotation is checked to enable hoisting and lowering by a hydraulic motor, separately from a winch drum among a ring gear and a carrier of a planetary speed reduction mechanism connected to the motor.

CONSTITUTION: A planetary speed reduction mechanism 20 connected to an output shaft of a motor 10 is composed of a ring gear 21 fixed to the inner peripheral surface of a winch drum 30, a sun gear 22 connected to an output shaft 10a of the hydraulic motor 10, a planetary gear 23 to mesh with these and a carrier 24 connected to the planetary gear 23, and is constituted in such a way that when the sun gear 22 is rotated in a condition of checking rotation of the carrier 24, the planetary gear 23 rotates, and rotates the ring gear 21, and rotates the winch drum 10. A torque detecting means 50 composed of a shaft 51 connected to this carrier 24 by a spline, a lever 52 rotatable integrally on the shaft 51 and a load cell 53 on the tip, is provided, and torque of the carrier 24 is detected.