To provide a method and apparatus for forming a tubular material with which a projecting shape such as bulging, a rib, etc. can be easily formed not only on a straight-tube-like tubular material, but also on a bent tubular material, and reduction and expansion in diameters, cutting, etc. are made possible with a simple structure.

By fixing the tubular material P by bringing outer peripheral die members 12, 13 into close contact with the entire periphery of the outer peripheral surface of the tubular material P and rolling the inner peripheral part of an inner peripheral die member 47 in the peripheral direction of the inner peripheral surface of the tubular material P while bringing the outer peripheral part of the roller-shaped inner peripheral die member 47 into pressure-contact with the inner peripheral surface of the tubular material P from the inside in the radial direction toward the outside, and fitting an annular forming projecting part 58 which is extended in the peripheral direction and formed in the outer peripheral part of the inner peripheral die member 47 into an annular forming recessed part 57 extending in the inner peripheral direction which is formed in the inner peripheral parts of the outer peripheral die members 12, 13, the diameter of a portion of the tubular material P is expanded.