PURPOSE: To improve operatability while eliminating inconvenience at the time of actuator concurrent operation, by changably setting the proportion of the operation stroke quantity of a control valve to the unit operating quantity of a pilot valve.

CONSTITUTION: An oil pressure circuit is provided with such a flow diverting function as automatically by adjusting the discharge flow rate of an oil pressure pump according to the required flow rate of an actuator so as to make load control, and each control valve is provided with such a flow diverting function as arranging a pressure compensation valve after passing a throttle valve so as to supply the pressure oil in parallel. As the oil pressure pilot operating mechanism of this circuit, a lever 17 and its pilot valve 18 for a bucket boom, a lever 19 and its pilot valve 20 for arm-rotating, and a lever 21 and its pilot valve 22 for switching are equipped. Moreover, an adjusting means C, composed of a variable throttle valve 23, a variable throttle valve 24, connected to the pressure oil passage downstream side of the variable throttle valve 23, a proportional pressure reducing valve 25 are provided on every oil pressure path respectively for connecting the pilot valves to the control valves, so as to adjust a swing speed ratio to lever operation.