To enable the compensation for heavier load by weakening a degree of pressure compensation in compensating for the pressure corresponding to the differential pressure by detecting the differential pressure between before and after an operating valve; Conversely, to enable the overcompensation by strengthening the degree of the pressure compensation; Thereby, to improve the lever operability and supply a great deal of pressure oil for the high load side.

The controller calculates a correction factor by such a correction amount that the greater the detected differential pressure between before and behind the operating valve becomes, the bigger the throttle degree of a corresponding opening area of the operating valve makes. The calculated correction factor is corrected and the operating amount of the operating lever is corrected using the correction factor so that the smaller the operating amount of a specific operating lever is for example, the operating amount of the operating lever for the operating valve in the minimum differential pressure is the correction amount corresponding to the degree of the differential pressure is reduced, that is, the throttle degree of the opening area of the operating valve is reduced.