PURPOSE: To prevent a corner part of a work from expanded consumption and having down of cut-edge and to improve machining precision by a method wherein the time when a wire electrode changes its direction is detected and an oscillating amplitude or stopped.

CONSTITUTION: A work table 3 is moved by an X- and Y-drive motor 13, 14 through signals of an NC unit 15. A work 1 undergoes electrical discharge machining by a wire electode 2 and the wire electrode 2 is oscillated by an oscillator 8 such as a quartz and the like through a horn 9, a contactor 10. This oscillating energy is broken switch 12. The ratio of the total counts given to motors 13, 14 from the NC unit to the count given to the X-axis motor 13 is operated by a comparison circuit 23 where the ratio is 1 for the straight line machining and the switch 12 is closed while the ratio is 0 for the curved machining and the switch 12 is open.