A method for working part with straight surface concave slot with left and right inclined structures, characterized mainly in that: in order to working, a skew angle of the tool is firstly adjusted, the workpiece and the Cartesian coordinate system of the tool are continuously relatively revolved until a projection of a tool axis on an X-Y surface is positioned in parallel with an assumed main axis of the coordinate system, respective surface recesses are worked by relative sliding motion of the tool and the workpiece especially in the direction of the Z axis in the case of the skew angle of 0 deg. and by relative sliding motion especially on all the three axes of the mechanical coordinate system in the case of the skew angle of +->0 deg., and this tool is engaged along one side surface due to a positive skew angle and along a side surface positioned mirror-symmetrically on the opposite side due to a negative skew angle. |