2 with the box in case the difference between the load pressure of the two actuator caused the saturation in the large composite operation, preventing the closing of the low-load apcheuk pressure compensating valve for preventing the reduction, stopping the actuator of low load apcheuk, the two actuators in the case of a load pressure difference caused the saturation, particularly in large complex operations, in order to secure the amount of pressure oil necessary for a high-load apcheuk actuator to prevent the reduction, stopping the high load apcheuk actuator, the parallel flow path (41f, 41g, 41h) the arrangement of the selector valve (100f, 100g, 100h) to decrease the passage area of ​​the parallel flow path (41f, 41g, 41h) when a is operated, an operating device for driving (34a, 34b) each.