HYDRAULIC BRAKE SYSTEM

An outflow of working fluid from a master cylinder to a brake cylinder is prevented when a brake pedal is not operated. Two pressure chambers 72, 70 of the master cylinder 62 and brake cylinders 42FL, FR provided respectively for front left and right wheels 2, 4 are respectively connected directly to each other by master passages 74, 76. Provided respectively in the master passages 74, 76 are master cut-off valves 194FL, FR each as a normally-closed electromagnetic open/close valve. As a result, when the brake pedal 60 is not operated and when no current is supplied to solenoids of the respective master cut-off valves 194FL, FR, the pressure chambers 72, 70 and the brake cylinders 42FL, FR are respectively disconnected to each other, preventing an outflow of the working fluid from the pressure chambers 72, 70, i.e., fluid chambers 82, 80 of a master reservoir 78 to the brake cylinders 42FL, FR.