A hydraulic brake apparatus for a vehicle includes a brake operating member, a hydraulic pressure generating source, a regulating valve, a master cylinder having first and second pistons, a pressure detecting means connected to a second pressure chamber for detecting a brake hydraulic pressure outputted from the second pressure chamber, a brake operating amount detecting means for detecting an operating amount of the brake operating member, and a judging means for judging a hydraulic pressure condition of first and second hydraulic systems respectively connected to first and second chambers based upon the brake hydraulic pressure detected by the pressure detecting means relative to the operating amount of the brake operating member detected by the brake operating amount detecting means.