Disclosed herein is a hydraulic unit of a brake system. According to one embodiment of the present invention, the hydraulic unit of a brake system includes a master cylinder configured to generate a hydraulic pressure to supply a braking hydraulic pressure to a wheel cylinder of a vehicle, a valve block coupled with the master cylinder to transmit the braking hydraulic pressure to the wheel cylinder and having a plurality of valves and borers, and an electronic control unit (ECU) installed at the valve block to control the plurality of valves, wherein a plurality of oil passages configured to connect the bores with hydraulic ports formed at the master cylinder are formed on a surface of the valve block to have straight lines and curved lines, and the plurality of oil passages are engraved on the surface of the valve block.