Disclosed herein is a pulsation damping device of a hydraulic brake system. The pulsation damping device of a hydraulic brake system which attenuates a pressure pulsation of brake oil discharged from a pump, the device comprises a damping portion installed to be inserted into a bore in communication with an inport into which the brake oil flows and an outport through which the brake oil is discharged, and a cap coupled to one end of the bore to block the one end, wherein a flow path is formed on an outer circumferential surface of the damping portion to guide the brake oil introduced into the inport to be discharged through the outport, and the flow path is formed in a longitudinal direction of the damping portion to be continuously connected from the inport to the outport.