PURPOSE: To eliminate the limitation of length in tube manufacturing by holding a plug in a tubing due to the balance of the rolling load of inclined roll and the coefficient of friction between the tubing and the plug in the cross helical rolling of seamless tube.

CONSTITUTION: In a device which the tubing is screwing moved with plural inclined rolls 1 and guide members for tubing which are alternately arranged around the pass line X-X of tubing, the plug 2 is floatablly fitted and supported on the pass center in the tubing due to the rolling load of inclined rolls 1 and frictional force that is acted between the inner periphery of tubing and the plug. The tubing is subjected to elongating rolling accompanied with the reduction of diameter while controlling the inner surface of tubing with this plug 2. In this way, the length of tube manufacturing isn't limited due to the length of mandrel bar for supporting the plug 2 and the effect of space saving with the nonuse of mandrel bar can be obtained.