This invention is to provide a brake system and a brake device for use of automobiles, in which a braking energy stored in an auxiliary pressure source can be exploited effectively for a braking purpose, even if an electrical system fails. In particular, the vehicle brake system includes a proportional pressure control valve 80 for generating braking liquid pressure by adjusting the braking energy stored in the auxiliary pressure source 30. Also the vehicle brake system comprises a passage 75 transmitting the liquid pressure generated by a stroke of a brake pedal 1, a switching valve 76 opening the passage in the powered condition and closing the same in the off-powered condition, and an auxiliary control portion 81 activating the proportional pressure control valve 80. Even in the off-powered condition, the high pressure accumulated in the auxiliary pressure source 30 can be used to adjust the required braking liquid pressure at the proportional pressure control valve 80. The switching valve 76 cane be replaces with a relief valve 116 and a return valve 117 for activating the proportional pressure control valve 80 so as to effectively utilize the high pressure of the auxiliary pressure source 30 even in the on-powered condition.