An electronic brake system comprising: a hydraulic-pressure supply device configured to generate a hydraulic pressure by operating a hydraulic piston using an electric signal that is output in response to a displacement of a brake pedal, and include not only a first pressure chamber formed at one side of the hydraulic piston movably disposed in a cylinder block, but also a second pressure chamber formed at the other side of the hydraulic piston; and a hydraulic control unit configured to include not only a first hydraulic circuit to control a hydraulic pressure applied to two wheel cylinders, but also a second hydraulic circuit to control a hydraulic pressure applied to two other wheel cylinders, wherein the hydraulic control unit includes: a first hydraulic passage configured to communicate with the first pressure chamber; second and third hydraulic passages (212, 213) branched from the first hydraulic passage, and respectively connected to the first and second hydraulic circuits (212, 213); a fourth hydraulic passage connected to the second hydraulic passage while communicating with the second pressure chamber; a fifth hydraulic passage configured to connect the second hydraulic passage to the third hydraulic passage; and a sixth hydraulic passage configured to connect the second hydraulic passage to the fifth hydraulic passage, characterized in that the hydraulic control unit further includes: first and second valves (231; 232, 332) provided in the second hydraulic passage to control flow of a pressure medium, a third valve provided in the third hydraulic passage to control flow of a pressure medium; a fourth valve provided in the fourth hydraulic passage to control flow of a pressure medium; a fifth valve disposed between one position connected to the sixth hydraulic passage on the fifth hydraulic passage and another position connected to the second hydraulic passage on the fifth hydraulic passage; a sixth valve disposed between one position connected to the sixth hydraulic passage on the fifth hydraulic passage and another position connected to the third hydraulic passage on the fifth hydraulic passage; and a seventh valve provided in the sixth hydraulic passage. a hydraulic-pressure supply device configured to generate a hydraulic pressure by operating a hydraulic piston using an electric signal that is output in response to a displacement of a brake pedal, and include not only a first pressure chamber formed at one side of the hydraulic piston movably disposed in a cylinder block, but also a second pressure chamber formed at the other side of the hydraulic piston; and a hydraulic control unit configured to include not only a first hydraulic circuit to control a hydraulic pressure applied to two wheel cylinders, but also a second hydraulic circuit to control a hydraulic pressure applied to two other wheel cylinders, wherein the hydraulic control unit includes: a first hydraulic passage configured to communicate with the first pressure chamber; second and third hydraulic passages (212, 213) branched from the first hydraulic passage, and respectively connected to the first and second hydraulic circuits (212, 213); a fourth hydraulic passage connected to the second hydraulic passage while communicating with the second pressure chamber; a fifth hydraulic passage configured to connect the second hydraulic passage to the third hydraulic passage; and a sixth hydraulic passage configured to connect the second hydraulic passage to the fifth hydraulic passage, characterized in that the hydraulic control unit further includes: first and second valves (231; 232, 332) provided in the second hydraulic passage to control flow of a pressure medium, a first hydraulic passage configured to communicate with the first pressure chamber; second and third hydraulic passages (212, 213) branched from the first hydraulic passage, and respectively connected to the first and second hydraulic circuits (212, 213); a fourth hydraulic passage connected to the second hydraulic passage while communicating with the second pressure chamber; a fifth hydraulic passage configured to connect the second hydraulic passage to the third hydraulic passage; and a sixth hydraulic passage configured to connect the second hydraulic passage to the fifth hydraulic passage, characterized in that the hydraulic control unit further includes: first and second valves (231; 232, 332) provided in the second hydraulic passage to control flow of a pressure medium, a third valve provided in the third hydraulic passage to control flow of a pressure medium; a fourth valve provided in the fourth hydraulic passage to control flow of a pressure medium; a fifth valve disposed between one position connected to the sixth hydraulic passage on the fifth hydraulic passage and another position connected to the second hydraulic passage on the fifth hydraulic passage; a sixth valve disposed between one position connected to the sixth hydraulic passage on the fifth hydraulic passage and another position connected to the third hydraulic passage on the fifth hydraulic passage; and a seventh valve provided in the sixth hydraulic passage.