PURPOSE: To apply knurling work without deforming a material even in the case that the object workpiece material is of small external diameter or an easily deformable soft material, further to substantially reduce a load to a machine device in use, and further to attain automatic operation while detecting optimum control of rolling force and tool change timing.

CONSTITUTION: Two rolling tools 1, 2 are rotatably engaged with holding members 5, 6 arranged in 180° opposed positions. Action of a hydraulic piston part 7 is converted into a change of distance between the rolling tools 1, 2 through a guide piston 10 and a long groove 71, to apply knurling work to the periphery of a workpiece material 12. A knurling work part rising amount of the workpiece material 12 and the number of teeth are detected by a displacement detector, to detect tool change timing while controlling an oil pressure.