A fluting method for forming a flute in a workpiece while the workpiece is moved relative to a rotating tool by the combination of a rotating feed shaft with other feed shafts, the method comprising a machining process of relatively moving the rotating tool on a tool path that runs along the direction in which the flute extends and machining the workpiece using a rotating tool with a diameter that is smaller than the width of the flute. The machining process changes the relative position of the rotating tool with respect to the workpiece and performs machining multiple times so that the rotating tool makes internal contact with a circle that has the width of the flute being formed in the workpiece as the diameter.