PURPOSE: To dispense with deburring and to dispense with bi-washing by fitting a straight tube into a straight hole of a closed half die, fitting a projecting part of one mandrel of a force-fitting implement into the straight tube, allowing an inserted tube to abut on the tube end, force-fitting it and pushing in and bending the straight tube.

CONSTITUTION: In a block body which abuts on the whole surface except a tube end 5 of a bent tube and contains it and in which a straight hole 6 of the same diameter as the tube diameter of the bent tube extends out from the tube end of the bent tube 2, two picecs of half dies 3 in which the center plane containing the bent part of the bent tube 2 is the divided surface are formed, and the half die 3 is freely openable and closeable. A force-fitting implement 4 having two pieces of mandrels 12 having a projecting part 14 fitted into the tube and having an inserting part 13 which abuts on the tube end 5 and is fitted into the straight hole 6, respectively is provided. A straight tube 1 is fitted into the straight hole 6 of the closed half die 3, a projecting part 13 of one mandrel of the force-fitting implement 4 is fitted into the straight tube 1, the inserting part 13 is allowed to abut on the tube end, and the straight tube is pushed in and bent by the force-fitting implement 4. A projecting part of the other mandrel of the force-fitting implement is fitted into the other tube and, the inserting part is allowed to abut on the tube and, and the bent tube is formed.