An electric power steering system that applies steering assist force from an electric motor to a steered mechanism of a vehicle, the steered mechanism transmitting steering force to steered wheels, comprising: a steering torque detecting unit that detects a steering torque; a basic target current value setting unit that sets a basic target current value for the electric motor based on a detected steering torque value detected by the steering torque detecting unit; a vibration compensation value generating unit that generates a vibration compensation value for suppressing vibration, based on the detected steering torque value; a target current value computing unit that computes a target current value, based on the basic target current value set by the basic target current value setting unit and the vibration compensation value generated by the vibration compensation value generating unit; and a control unit that controls the electric motor based on the target current value computed by the target current value computing unit, characterized in that the vibration compensation value generating unit includes a low-pass filter that executes a low-pass filtering process on the detected steering torque value, and a unit that generates a vibration compensation value for leading the detected steering torque value to the detected steering torque value obtained through the low-pass filtering process, based on a deviation between the detected steering torque value that has not been subjected to the low-pass filtering process and the detected steering torque value obtained through the low-pass filtering process. a steering torque detecting unit that detects a steering torque; a basic target current value setting unit that sets a basic target current value for the electric motor based on a detected steering torque value detected by the steering torque detecting unit; a vibration compensation value generating unit that generates a vibration compensation value for suppressing vibration, based on the detected steering torque value; a target current value computing unit that computes a target current value, based on the basic target current value set by the basic target current value setting unit and the vibration compensation value generated by the vibration compensation value generating unit; and a control unit that controls the electric motor based on the target current value computed by the target current value computing unit, characterized in that the vibration compensation value generating unit includes a low-pass filter that executes a low-pass filtering process on the detected steering torque value, and a unit that generates a vibration compensation value for leading the detected steering torque value to the detected steering torque value obtained through the low-pass filtering process, based on a deviation between the detected steering torque value that has not been subjected to the low-pass filtering process and the detected steering torque value obtained through the low-pass filtering process. a low-pass filter that executes a low-pass filtering process on the detected steering torque value, and a unit that generates a vibration compensation value for leading the detected steering torque value to the detected steering torque value obtained through the low-pass filtering process, based on a deviation between the detected steering torque value that has not been subjected to the low-pass filtering process and the detected steering torque value obtained through the low-pass filtering process.