An electric brake system is disclosed. The electric brake system comprises a hydraulic pressure supply device configured to generate hydraulic pressure using a hydraulic piston which is activated by means of an electrical signal that is output corresponding to a displacement of a brake pedal, and including a cylinder block, first and second hydraulic pistons movably accommodated inside the cylinder block, and first and second pressure chambers comparted by the first and second hydraulic pistons, a first hydraulic circuit configured to connect a first hydraulic flow path communicating with the first pressure chamber to one or more wheel cylinders, a second hydraulic circuit configured to connect a second hydraulic flow path communicating with the second pressure chamber to one or more wheel cylinders, and a balance valve configured to open and close a balance flow path connecting the first hydraulic flow path to the second hydraulic flow path.