A hydraulic circuit includes a pump driven by a motor, an inverter for controlling the motor, and an accumulator. The inverter controls rotational speed of the motor such that the pump always discharges hydraulic fluid at a fixed flow rate, which is the sum of an average necessary flow rate and an adjustment flow rate. The accumulator operates, when the fixed flow rate and a necessary flow rate differ, in order to accumulate or discharge the hydraulic fluid to thereby secure the necessary flow rate.