PURPOSE: To greatly improve the working efficiency by using the same tool in a single set of work machine to perform milling work and turning work, in the case of preliminary work of fillet roll work in a crankshaft.

CONSTITUTION: A milling cutter 6, in which many chips 7 having a circular arc-shaped protrusion are mounted in the corner part, is rotated, and milling work in a polygonal shape is applied to the peripheral surface of a journal 2 or a pin 3 of a crankshaft 1 rotated at a low speed. Next in a condition that rotation of the milling cutter 6 is stopped with the crankshaft 1 rotated, turning work of a smooth circular arc-shaped groove is applied to a corner thickness part 5 of the journal 2 or the pin 3 by the circular arc-shaped protrusion in the corner part of the chip 7 similarly to a tool, so that fillet roll work can be immediately performed. By using the same tool in a single set of work machine for preliminary work of the fillet roll work, work efficiency can be remarkably improved.