A controller of an electrical discharge machine comprises: a control unit that controls a machining condition set by the electrical discharge machine; an acquisition unit that acquires a parameter indicating an electrical discharge state between poles in a state where the machining condition is controlled by the control unit so that a normal electrical discharge occurs between the poles; an arithmetic unit that obtains a probability density distribution of the acquired parameter; a decision unit that decides a threshold that specifies a boundary between a normal electrical discharge and an abnormal electrical discharge between the poles based on the obtained probability density distribution; and a discrimination unit that discriminates whether the electrical discharge state between the poles is normal or abnormal by using the decided threshold, and wherein the control unit controls the machining condition based on a discrimination result of the discrimination unit.