PURPOSE: To perform operations smoothly and efficiently by a method in which a mode switcher to operate an electromagnetic valve for bucket by a boom control signal is provided and the bucket is operated in the opposite direction to the vertically moving direction of the boom.

CONSTITUTION: Solenoids 13 and 14 for rising and lowering and solenoids 15 and 16 for scooping and dumping are provided for proportional electromagnetic valves 11 and 12 for controlling boom and bucket. The solenoids are excited to operate the valves 11 and 12. A mode switcher is turned on by pushing, and when an operating lever is moved forwards by rocking movement, pulse signal H1 from AND circuit 40a is put in a field-effect transistor 42b to raise 13 the boom. At the same time, the bucket is put to dumping action 16. Also, when the lever is moved backwards by rocking movement, signal H2 from AND circuit 41a is put in a transistor 43, and at the same time as the boom is lowered 14, the bucket is put to scooping action 15 concurrently.