PURPOSE: To perform easily the working of a small tube having a big difference in diameter without causing a vibration in the contraction of tube by inserting a blank tube on a core metal and by executing a blank drawing work and stroke work having multicycles using plural work rolls.

CONSTITUTION: One end of a blank tube 1 is inserted onto a metal core 6 and fixed to a chuck 13 together with the core metal 6 and the other end of the blank tube is made a free end. A rough form part 15 is formed by arranging a work roll 10 symmetrically in plural pieces, by performing the reciprocation in the direction of an axis Y and encroachment in the direction of axis X synchronously and by performing a blank drawing with a drawing roll 11. The rough form part 12 is formed for finishing to a small tube 4 having the prescribed thickness with the execution of a stroke work due to the encroachment of the work roll 10 in axial X direction and reciprocation in the axial Y direction, when the inner diameter of the rough form part 15 is brought into contact with the small diameter part of the core metal 6. A small tube in long length can be thus formed easily without the generation of vibration and distortion.