To implement the machining of a bevel gear as designed.

There is provided a method for machining the bevel gear by using a machine tool having a cutter including a plurality of gear cutting blades. The method is carried out based on an operational program which calculates output data on machining conditions of a workpiece and on the geometric dimension of the finished bevel gear after machining based on input data on functional design specifications of the bevel gear. After inputting the design specifications and calculating the first output data, the workpiece is machined under machining conditions different from conditions based on the output data, and an error between the geometric dimension of the bevel gear machined under the different machining conditions and the geometric dimension of the bevel gear according to the output data is measured. Further, the different machining conditions and the error are inputted into the operational program to calculate data on new machining conditions, and then the workpiece is machined under the new machining conditions.