Abstract: A wire-extension end detector having high operational reliability is provided for use with a wire-cut electric discharge machine. As a wire comes between a wire drive roller and a pinch roller during a wire extension, it is conveyed by rotation of the rollers. As the wire travels, a disc (4c) integral with a tension brake roller driven by the running wire is rotated. A signal processing circuit (24) receives and delivers a pulse train output from a photoelectric switch (5) in accordance with a black-and-white code pattern on a rotating disc coupled thereto, and generates an H-level output indicative of the end of wire extension. If the wire extension fails, an H-level output from the signal process circuit is not output and a wire extension is carried out again.