A method of animation plotting by an NC machining program on an NC lathe having a multiplicity of tool rests. The method provides animation plotting for Y-axis machining such as engraving. A display screen of a CRT/MDI provides first display areas "a1" to "an" for simulating a machining process of a workpiece projected in an axial direction of a tool. A second display area is also provided for simulating a machining process of the workpiece projected in the direction of a Y-axis orthogonal to an X-axis and a Z-axis. For each rotational positioning point .theta.i (i=1 to n) of the spindle, Y-axis machining is simulated by simultaneously displaying the movement path of the tool and the shape of the tool within the first display area "ai" and the second display area.