A hydraulic circuit for a working machine

PROBLEM TO BE SOLVED: To provide a hydraulic circuit of a work machine, the hydraulic circuit providing excellent feeling of slewing operation.SOLUTION: The hydraulic circuit of a work machine according to the present invention comprises: a prime mover whose number of revolutions is determined based upon an operation command; a variable displacement hydraulic pump driven by the prime mover; a slewing motor driven with discharged oil from the variable displacement hydraulic pump; and a control valve controlling pressure oil supplied from the variable displacement hydraulic pump to the slewing motor. Further, the hydraulic circuit comprises: a number of revolutions signal generation part which generates the number of revolutions signal indicative of the number of revolutions of the prime mover; and a flow rate control valve controlling the flow rate of the pressure oil guided from the variable displacement hydraulic pump to the control valve, the flow rate control valve being configured to control the differential pressure across the control valve to a value corresponding to the number of revolutions of the prime mover according to the number of revolutions signal that the number of revolutions signal generation part outputs.SELECTED DRAWING: Figure 2