An electric brake system is disclosed. The electric brake system includes a hydraulic pressure supply device configured to generate hydraulic pressure using a piston that is activated by means of an electrical signal output corresponding to a displacement of a brake pedal, and including a first pressure chamber provided at one side of the piston, which is movably accommodated inside a cylinder block, and connected to one or more wheel cylinders, and a second pressure chamber provided at the other side of the piston and connected to one or more wheel cylinders, a first hydraulic circuit including a first hydraulic flow path communicating with the first pressure chamber, and first and second branching flow paths that branch from the first hydraulic flow path to be connected to two wheel cylinders, respectively, a second hydraulic circuit including a second hydraulic flow path communicating with the second pressure chamber, and third and fourth branching flow paths that branch from the second hydraulic flow path to be connected to two wheel cylinders, respectively, and first to fourth inlet valves configured to control an opening and closing of the first to fourth branching flow paths, respectively.