To obtain a flange forming apparatus of a tubular material which is miniaturized by simplifying the structure.

This apparatus is provided with a forming roller (10) which is rotatable around the axial center orthogonally crossed with the center of rotation of a main spindle (6) in the end part of the main spindle (6), also the forming surface (11) which is continued from the side of one end of the outer periphery of the forming roller (10) toward the side of the other end, the side of the one end is made into a small diameter and the side of the other end is made into a large diameter, also a roller moving device (15) for moving the forming roller (10) in the direction in which the small diameter side of the forming surface (11) is advanced on the axial center of rotation of the forming roller (10) and a work holding device (25) for holding a work approximately on the same axle as the main spindle (6) by projecting the one end (35a) of the tubular material (35) in the front of the main spindle (6) in its direction.