Disclosed herein is an electrically controlled brake system. The electrically controlled brake system includes a motor and a pump, a master cylinder, a reservoir that is coupled to an upper portion of the master cylinder and in which a brake fluid is stored, an accumulator in which a brake fluid pumped from the reservoir is stored by the motor and the pump, a hydraulic path that connects the accumulator and each of wheel cylinders, an apply valve and a release valve that are provided on the hydraulic path and control a hydraulic pressure transferred from the accumulator to each of the wheel cylinders, a pedal simulator including a simulation chamber connected to the master cylinder and configured to store a brake fluid flowing from the master cylinder to provide a reaction force of a brake pedal, and a simulation valve provided at an inlet of the simulation chamber, a backup path that is connected to the hydraulic path and connects the master cylinder and each of the wheel cylinders, a cut valve that is provided on the backup path and blocks the backup path, a first pressure sensor that is provided on the backup path and detects a pressure of the pedal simulator, a second pressure sensor that is provided on the hydraulic path and detects a pressure of the hydraulic path and an electronic control unit (ECU) that determines whether a mechanical leak failure of the cut valve occurs using a correlation between the pressure of the pedal simulator detected by the first pressure sensor and the pressure of the hydraulic path detected by the second pressure sensor.