In an embodiment, an electric parking brake system is disclosed. The system may include or comprise a pair of parking cables each connected to a brake. Additionally, the system may include or comprise a motor and a drive gear. The system may also include or comprise a planetary gear unit including or comprising a sun gear connected to the drive gear, a plurality of planetary gears gearedly connected with the sun gear, an internal gear formed along a revolving path of the planetary gears, and an output carrier connected to the planetary gears. The system may further include or comprise a screw-nut unit including a screw member and a nut member screwed to the screw member, the screw-nut unit being connected to the output carrier, and the parking cables being connected to opposite ends of the screw-nut unit, respectively.