Disclosed is an electronic parking brake system, which is configured to push first and second brake shoes respectively disposed on inner opposite sides of a drum to an inner surface of the drum for braking, including an actuator including a motor configured to rotate forward and reverse to generate a driving force for braking, and a reduction gear unit configured to amplify the driving force transmitted from the motor, and a power converter configured to convert a rotational motion from the actuator into a linear motion to press or release the first and second brake shoes.