A method of truing a grinding wheel capable of accurately truing the wheel surface of the grinding wheel in a short time in a grinding device having the conductive grinding wheel, comprising the steps of, when the flat annular grinding wheel surfaces (10a, 10a) of a pair of grinding wheels (1, 2) disposed opposedly to each other are trued simultaneously, for example, disposing a discharge truing electrode (20) between the grinding wheel surfaces (10a, 10a) of both grinding wheels (1, 2) and traversing the electrode parallel with and relative to both grinding wheel surfaces (10a, 10a) while applying a discharge truing to the grinding wheel surfaces in the state of no-contact with both grinding wheel surfaces (10a, 10a) by a discharge action between the discharge truing electrode (20) and both grinding wheel surfaces (10a, 10a).