PURPOSE: To execute the cutting of the tube end of a bent tube so as to prevent generation of defective weld, and to execute the assembly to a correct length.

CONSTITUTION: A tube cutting device consists of a tube rotating/supporting part 1 where a fixed tube receiving roller 7 is fixed to one end side of two parallel shafts 5 which are rotatably supported, and a moving tube receiving roller 8 is movably mounted in the axial direction on the other end side of the parallel shafts 5, a driving part 10 provided with a variable speed mechanism to rotate one of the parallel shafts 5, and a gas cutter 16 having a cutting torch 17 where the blowing-out angle of the gas is variable and the height of a tube 2 supported by the tube rotating/supporting part 1 from the wall surface is kept constant.