Disclosed is a check valve of a hydraulic brake system. The check valve includes a valve housing which includes a tapered front end having a smaller diameter than a middle end, the cylindrical middle end extending from the front end by a predetermined length to allow the ball and spring to be accommodated within the middle end, a rear end stepped from the middle end to have a greater diameter than the middle end, and a flange circumferentially bent from the rear end to have a greater diameter than the rear end, and a valve seat having an outer diameter equal to an inner diameter of the rear end so as to be press-fitted into the rear end of the valve housing. The check valve having a simplified configuration achieves size and weight reduction and is manufactured at low cost and high processing efficiency using pressing.