To provide a method for locally increasing the thickness of a tubular body in which the external dimensions of a wall-thickness increased part are uniform, its outer surface is smoothed, and the wall-thickness increased part is fairly thick.

An intended part of a tubular body 1 is heated, an outer die 25 where annular wall-thickness increased parts 27A, 27B are formed is located on an outer surface 1a at the heated part, the compressive force is given in the longitudinal direction of the tubular body at the heated part, and a part of the material at the heated part is press fitted into the wall-thickness increased parts 27A, 27B. The outer surface 2a of the wall-thickness increased part 2 in the heated condition can be trimmed by the wall-thickness increased parts 27A, 27B, and the outer surface of the wall-thickness increased parts can be uniformed in outer dimensions and smoothed. Because the wall-thickness increased parts 27A, 27B are provided with recessed annular ring part forming surfaces 29A, 29B, the ring part can be projected as soon as the wall-thickness increased parts are formed, and the outer surface of the ring part can be trimmed.