To provide a hydraulic control circuit of a utility machine which accurately supplies a working fluid flow rate required for an attachment by using a simple constitution, and improves an interlocking property with the other hydraulic actuator.

A flow control valve 1 capable of changing the degree of an opening is interposed on a first hydraulic circuit L1 for connecting an actuator 20a for the attachment and a hydraulic pump 11 to each other. Attachment pressure compensating valves 3a, 3b are interposed on upstream sides of the control valves 6a and 6b of the first hydraulic circuit L1, respectively. Furthermore, a pilot control valve 5b adjusting pilot pressure is mounted, and thus, the flow control valve 1 is regulated by the pilot control valve 5b, so as to maintain a constant differential pressure between the upper-stream pressure of the attachment pressure compensating valves 3a, 3b and the loaded pressure in the first control valve.