A brake device can prevent deterioration of braking force by applying a predetermined pressure in the drive hydraulic pressure chamber even when an electric system failure occurs. The brake device includes a stroke simulator portion, regulator, a first passage connecting the accumulator and the high pressure port of the regulator, a second passage connecting the reservoir tank and the low pressure port of the regulator, a third passage connecting the stroke simulator portion and the pilot pressure input port of the regulator, a fourth passage connecting the drive hydraulic pressure chamber and the output port of the regulator and a fifth passage connecting the accumulator and the drive hydraulic pressure chamber bypassing the high pressure port. The normally open type pressure decrease control valve is provided in the second passage or in the fourth passage whereas the normally closed pressure increase control valve is provided in the fifth passage.