An electric parking brake actuator has an actuator device, a brake device and a cable-tension measuring device. The brake device has a cable and a tube assembly. The cable is mounted through the actuator device. The tube assembly is mounted around the cable and has a first tube, a second tube, a spring, a Hall IC and a magnet. The cable-tension measuring device has a first member and a second member which are mounted around the cable. The second member is capable of moving toward the first member relatively. The compressible spring is mounted between and abuts the first member and the second member. The Hall IC and the magnet are respectively mounted securely on the first member and the second member. The Hall IC is capable of measuring how much the spring is compressed to further measure the tension of the cable.