Wire electric discharge machining method and wire electric discharge machining apparatus

A wire electric discharge machining apparatus comprising a NC controller, wherein

• the NC controller comprises:
• a detection unit which detects a plate thickness of a workpiece in a rough machining step;
• a storage unit which stores the plate thickness as plate thickness information in association with divided regions obtained by dividing an XY-plane of a workpiece stand of the wire electric discharge machining apparatus into small regions;
• and a processing unit, wherein
• in an end surface finishing step, the processing unit sets a peripheral region comprising a current machining position of the workpiece as a search range, and with reference to the plate thickness information associated with the divided regions within the search range, estimates whether there is a level difference ahead of a traveling direction of a machining path according to the plate thickness information associated with the divided regions and a plate thickness of the workpiece at the current machining position;
• and the processing unit sets a peripheral region comprising a position of the level difference as a machining condition change range, and performs a control of changing the machining conditions when the current machining position of the workpiece enters the machining condition change range.