A hydraulic circuit for a construction machine which operates an actuator for working machine simultaneously with an actuator for working element without degrading the operation of the actuator for working machine. The hydraulic circuit comprises a first hydraulic pump, a first directional control valve connected to the first hydraulic pump and controlling an operation of the working machine actuator, a third directional control valve controlling an operation of the working element actuator, a second directional control valve connected to a second hydraulic pump, a first pilot operating device for controlling an operation of the first directional control valve and a second pilot operating device for controlling an operation of the third directional control valve. The hydraulic circuit further comprises a first hydraulic fluid joining device for providing hydraulic fluid of the second hydraulic pump to the input side of third directional control valve, a second hydraulic fluid joining device for supplying the hydraulic fluid of the second hydraulic pump to the input side of the first directional control valve, and a priority switching device for preventing, in response to a signal of the first pilot operating device, the signal of the second pilot operating device from being applied to the second directional control valve.