To produce a sofa with smaller number of component parts, efficiently, at a low cost, sturdily, and light in weight, by forming the framework through folding and welding of metal pipes.

The side end members 3 of the sofa framework having a seat bottom part 1 and seat back part 2 are formed from metal pipes. Between these side end members 3, metal pipes 4-7 in the form of straight pipe are parallel installed as stretching by welding in the positions between oversurface front parts of the seat bottom part 1, between its oversurface rear parts, and between the upper parts of the seat back part 2. On the seat back side of the seat bottom 1, metal plates 8 as shape holder are inserted and fastened, and a metal pipe 9 is installed as stretching by welding between the bottoms of this metal plate 8, and a number of thin bands of metal 10 are welded between the metal pipes 4 and 5 and the ones 5 and 6 so that the intended sofa framework 11 is built.