A method of controlling a wire electric discharge machine, which applies a highfrequency voltage to a machining gap between a wire electrode and a workpiece located at a predetermined distance from the wire electrode, thereby generating electric discharge to machine the workpiece, the wire electric discharge machine comprising: machining-gap voltage detection means for detecting a machining-gap voltage produced In the machining gap; voltage application means configured to apply a bipolar voltage to the machining gap between the wire electrode and the workpiece for a period of one microsecond or less with a quiescent time longer than the duration of voltage application between each two adjacent cycles of voltage application provided; duty cycle number counting means (7, 77) configured to count the number of duty cycles of the voltage applied by the voltage application means for each unit time; open-circuit state identification means (7, 76) configured to identify an open-circuit state where no electric discharge occurs after the voltage is applied, based on the machining-gap voltage detected by the machining-gap voltage detection means; and open-circuit number counting means (7, 78) configured to count the number of open-circuits identified by the open-circuit state identification means for each unit time, and wherein an electric-discharge ratio is obtained from an open-circuit ratio, which is calculated based on the number of duty cycles per unit time counted by the duty cycle number counting means (7, 77) and the number of open-circuits per unit time counted by the open-circuit number counting means (7, 78), and an experimentally determined dependency of electric-discharge and short-circuit ratios on the open-circuit ratio within unit time, and by obtaining a frequency of electric discharge per unit time or distance based on the counted number of duty cycles per unit time and the obtained electric-discharge ratio. machining-gap voltage detection means for detecting a machining-gap voltage produced In the machining gap; voltage application means configured to apply a bipolar voltage to the machining gap between the wire electrode and the workpiece for a period of one microsecond or less with a quiescent time longer than the duration of voltage application between each two adjacent cycles of voltage application provided; duty cycle number counting means (7, 77) configured to count the number of duty cycles of the voltage applied by the voltage application means for each unit time; open-circuit state identification means (7, 76) configured to identify an open-circuit state where no electric discharge occurs after the voltage is applied, based on the machining-gap voltage detected by the machining-gap voltage detection means; and open-circuit number counting means (7, 78) configured to count the number of open-circuits identified by the open-circuit state identification means for each unit time, and wherein an electric-discharge ratio is obtained from an open-circuit ratio, which is calculated based on the number of duty cycles per unit time counted by the duty cycle number counting means (7, 77) and the number of open-circuits per unit time counted by the open-circuit number counting means (7, 78), and an experimentally determined dependency of electric-discharge and short-circuit ratios on the open-circuit ratio within unit time, and by obtaining a frequency of electric discharge per unit time or distance based on the counted number of duty cycles per unit time and the obtained electric-discharge ratio.