Control circuit for hydraulic actuator

A control circuit for a hydraulic actuator which allows the hydraulic actuator to be operated readily without much skill and at a suitable speed in accordance with a load applied thereto. The control circuit includes a change-over valve provided intermediately of a pilot pipe line communicating with a pilot oil chamber of a hydraulic change-over valve which belongs to one of a pair of hydraulic change-over valve sets of a hydraulic operating circuit for the hydraulic actuator. The change-over valve is normally urged to a position wherein the pilot oil chamber of the hydraulic change-over valve is communicated with a tank, but is changed over, when a hydraulic pressure higher than a predetermined value acts upon a pilot oil chamber of the change-over valve, to another position in which the pilot oil chamber of the hydraulic change-over valve is communicated with the pilot pipe line. A branch pipe line branches from a pipe line for discharge oil under pressure of a hydraulic pump provided for supplying oil under pressure to the other hydraulic change-over valve set and is connected to the pilot oil chamber of the change-over valve.