PURPOSE: To provide the producing method of a flare tube with an expanded end of tube which can easily expand the end even if the tube has any size of diameter and the device therefor.

CONSTITUTION: This is a device to produce a flare tube has the expanded end of a tube, the device is composed of a rotary body 2 to rotate almost matching to the center C of the tube 1, at least two expanding tools 3 which are attached symmetrically to the rotary body 2, which have the rotary center of gravity 4 in the outside of the tube and which have truncated cone like rollers 3b, and stoppers 7 to position the expanding tool 3 matching to the internal diameter of tube. Therefore, the flare tube can be produced without requiring many tools or many heating devices.