PURPOSE: To bring a bucket to a horizontal position, by a method wherein inclining angles of a boom, an arm, and a bucket are detected, the horizontal holding set angle of the bucket is set, an angle of a bucket opening is compared with said set angle, and a valve is electrically controlled so that a deviation attains zero.

CONSTITUTION: In a power shovel in which a boom 2, an arm 4, and a bucket 6 are individually rockably operated by their respective hydraulic cylinders, manual switch-operated electric switching valves for operating their respective hydraulic cylinders are mounted, and inclining angles θA, θB, and θC are detected to find the angle of the opening of the bucket. The result is compared with a set value set approximately in parallel to the angle of the bucket opening, and a hydraulic switching valve for operating the bucket is electrically actuated according to the deviation value to bring the deviation value to zero. This causes the bucket opening part to be held in an approximately horizontal state, and reduces spilling of earth and sand at a loading time of earth and sand.