To provide a working method capable of shortening the working time and enhancing the working accuracy when continuously working a helical gash S on a long workpiece 16.

A two-spindle-facing type NC composite lathe 100 with both spindles 11a and 11b having a function of controlling an angle is employed to alternately hold the long workpiece 16 between the spindles 11a and 11b for sequentially feeding and drawing the long workpiece 16 in an axial direction, and to expose a preceding lathed portion and sequentially lathe the preceding lathed portion. Thus, the working time for working the continuous helical gash S on the long workpiece 16 can be shortened. In addition, no shift in the center, a position or an angle due to the switching occurs, and both sides of the workpiece can be chucked at a proper carrying interval according to a thickness of a spindle core for working, deflection, distortion, twisting or the like of the workpiece can be suppressed, thereby improving working accuracy.