The present invention relates to a hydraulic pressure control device for construction machinery, comprising: a pilot pump; a swing motor for rotary-actuating an upper turning body; a brake control valve for controlling the direction of a hydraulic pressure of the pilot pump to operate a brake; a controller for receiving a command signal for driving the swing motor and applying the command signal to the brake control valve; a relief valve interposed between the brake control valve and the pilot pump; and a drain control valve, disposed in parallel with the brake control valve, for performing opening and closing operations so that the hydraulic pressure of the pilot pump can selectively return to a hydraulic tank in accordance with the state of the brake control valve, the drain control valve being opened for the hydraulic pressure to be discharged to the hydraulic tank without passing through the relief valve if the brake control valve is switched to brake the swing motor.
