PURPOSE: To eliminate the need for a load detector and a signal cable, and to simplify device constitution by bringing a servomotor to the state of servo- locking, stopping a cage and estimating and arithmetically operating the weight of freight loaded on the cage.

CONSTITUTION: A lifting-lowering type conveyor 1 operates a hoist 2 by a servomotor 42, loads freight on a cage 3 and conveys the cage in the vertical direction. The servomotor 42 is controlled, the freight is positioned at a place to be loaded, the servomotor 42 is brought to the state of servo-locking, and the cage 3 is stopped. The required torque of the servomotor 42 before and after the freight is placed on the cage 3 at the place is measured, and the weight of the freight is estimated and arithmetically operated. Accordingly, the freight is carried when weight is kept within a specified upper limit value.