When a wire electrode is arranged along a traveling path by manual operation, a motor M1 for feeding the wire electrode to a workpiece is driven in response to a predetermined torque command from a control section with a switch SW1 on a side a. The wire electrode is connected, and a motor M2 for delivering the electrode from the wire is driven at a predetermined speed, whereby the electrode is run. Then, the switch SW1 is shifted to a side b and a switch SW2 to the side a, and the motor M1 is subjected to torque control such that a tension on the wire electrode detected by a tension detector is equal to a command tension. When a variation of the tension on the wire electrode is converged, the switches SW1 and SW2 are shifted to the side b, speed control of the motor M1 is performed so that detected tension is equal to the command tension, and electric discharge machining is started.