ELECTRIC PARKING BRAKE SYSTEM

An electric parking brake system is provided to operate the electric parking brake system actively by modifying the connection structure of a motor generating driving force and a screw-nut unit converting rotation of a gear into linear motion. An electric parking brake system includes parking cables(41,42) connected to brakes applying braking force to wheels of a vehicle to operate the brakes, a motor(110) generating driving force for operating the parking cables, a driving gear(121) rotating by the motor, a first deceleration gear(131) engaged with the driving gear, a second deceleration gear(133) transmitting power to a connection shaft(132) combined with the first deceleration gear, a nut(142) combined with the second deceleration gear to transmit power and provided with a female screw part(142a), and a screw(143) having a male screw part(143a) thread-connected to the female screw part for linear motion. The parking cables are connected to ends of the nut and the screw, and an external gear(141) is integrally combined with the nut and engaged with the second deceleration gear.