To stop a drum by correctly detecting an upper limit detecting position and a lower limit detecting position of a belt sling.

A suspending tool 5 is connected with one end of a belt sling 3 of which the other end is wound on a drum 2 which is rotated and driven in the forward and backward directions, a detecting plate 6b is attached near the other end of the belt sling 3 to form a proximity sensor 7, for detecting the upper limit of the belt sling 3, and a micro-switch 8, and a helical torsion spring 9 for pressing a lever 8a when the tension of the belt sling 3 is small, are installed for detecting the lower limit.