Disclosed herein is a hydraulic brake system. The hydraulic brake system comprises a damping device configured to attenuate pressure pulsation of brake oil discharged according to a driving of a pump, wherein the damping device includes a sleeve fixed to a bore that is connected to a discharge end of the pump and having an opened one side, a damping piston slidably installed inside the sleeve, and an elastic member provided inside the sleeve and configured to elastically support the damping piston, and wherein a slot having a width which is varied is formed at an inner circumferential surface of the sleeve in a direction in which the brake oil flows so that a variable orifice is formed between the damping piston and the sleeve.