PURPOSE: To vary the dropping speed of a load to be lifted even with a device where a low pressure relief valve is incorporated in a hydraulic circuit by conducting the initial movement on the load side of a hydraulic actuator slowly and smoothly, and improve operationability at the time of operation on the load side.

CONSTITUTION: This controller for an hydraulic actuator 1 is provided with a low pressure relief valve 5 and a counter balance valve 4 in its circuit. The valve opening pressure of the low pressure relief valve 5 is made variable. Therefore, when an operating means 10 is operated to the same side as a load applied to the hydraulic actuator 1, the valve opening pressure of the low pressure relief valve 5 can be changed to the high pressure side.