An electric-discharge machining device including an electric-discharge-state determination unit that determines whether an electric discharging state between a machining electrode and a workpiece is either a state of normal electric discharge or of abnormal electric discharge, and a machining-condition switching unit that changes at least one machining condition, further includes a storage unit that stores therein an electric-discharge-state determination indicator, a standard-deviation calculation unit, and a boundary calculation unit that calculates a boundary to be applied to a determination in the electric-discharge-state determination unit based on the electric-discharge-state determination indicator, wherein the machining-condition switching unit changes the machining condition according to a comparison result between the standard deviation calculated by the standard-deviation calculation unit and a standard deviation reference set as a reference of the standard deviation.