To provide a necking forming method for the tube end of the oil well tube and a necking jig to be used for that purpose, by which the necking forming is possible by using a chamfering machine installed prior to thread cutting without requiring a dedicated machine for the necking forming.

This is the necking forming method for the tube end of the oil well tube 21, which is used for securing the thickness of a metal sealing part to be formed at the tip of a thread joint to be provided on the oil well tube 21. On the spindle head 13 of the chamfering machine 11 for performing the bevel working of the inside surface of the tube end of the oil well tube 21, the necking jig 1 equipped with plural swage rollers 6 is mounted, and the necking forming of the tube end of the oil well tube 21 is performed by the necking jig 1 by using the rotational force and the driving force of the chamfering machine 11.