PURPOSE: To groove stably a diametrally drawn pipe without breaking said pipe in the stage of grooving the inside surface of said pipe by means of a grooving plug and a planetary rotating roll by bringing gradually the roll into proximity to the plug.

CONSTITUTION: The pointed part of the metallic pipe 1 is successively passed through a drawing die 7, a rotary head 23 and a finishing die 17 and thereafter the pipe 1 is gradually advanced; at the same time, the head 23 is rotated. The floating plug 4 approaches to the drawing die 7 and reduces diametrally the pipe 1 and to hold the grooving plug in the home position. The pipe 1 is then moved at a prescribed speed and a wedge 19 is gradually retreated by the operation of an air cylinder 18 engaging with a die holder 22 to advance the die holder 22 toward the head 23. The plug 5 arrives at the position where the plug faces the planetary rotating roll 24. The pipe 1 reduced diametrally by the head 23 is forced up onto the plug 5 and is provided with prescribed grooves on the inside surface thereof.