To provide a groove forming roll for manufacturing a tube having grooves on the inside surface with which the plastic deformation and breakage of the roll itself are completely eliminated even if a pair of rolls themselves are subjected to abnormal and strong rolling force when the grooves are formed on one surface side of a bar stock of a metal plate by making the bar stock of the metal plate pass through between a pair of the rolls.

In the groove forming roll for manufacturing the tube having the grooves on the inside surface which is provided with a shaft core body 1, a ring-shaped body 2 consisting of a groove forming ring 21 forming the grooves on the surface that is fit on the outer peripheral side of the shaft core body 1 and two smooth rings on the surface of which the grooves are not formed and are superposed from both sides so as to hold the groove forming ring 21 between them and key with which the ring-shaped body 2 and the shaft core body 1 are fixed. The groove forming ring 21 is a groove forming ring without a key-way on the side of the inner peripheral surface of which the key-way is not provided.