To provide a hydraulic circuit for a working machine capable of independently traveling a carriage only by assembling a minimum set of equipment necessary for traveling, and dispensing with long time work and a wide working place for the assembling of the working machine and the repairing.

In this working machine having a hydraulically operatable working device on a carriage 42 provided with a hydraulically operatable traveling device, a hydraulic circuit for the traveling device comprising an HST pump 2, an HST charge pump 3, an HST motor 9, a pump 4 for steering the carriage, a carriage steering circuit 16 and an oil tank 31 for the traveling device, and a hydraulic circuit for the working device, comprising an oil tank 32 for the working device are independently mounted.