and set on the outer periphery of insert member 6 each insert member can perform the function of a gasket against the inner peripheral face of the body 2 the insert members 6 are each formed either by rolling a thick wall pipe or a thick wall plate then joining the opposed edges of the roll as by welding thereby giving rise to a metallic tube and cutting the tube by rolling or press working or by drawing a thick wall plate material into the shape shown in the diagram by the press working otherwise they may be formed by precision casting such as the lost wax process or by sintering a metallic powder further the insert members 6 contemplated by this invention possess such a thickness as to manifest fully satisfactory strength during the course of joining and also possess fully satisfactory strength to withstand the force exerted during the forced insertion into the pipe 1 that is the ball valve of this invention is directed toward allocating functions decreasing weight and compacting construction by adopting a configuration which derives the strength necessary for a pressure vessel mainly from the body 2 formed of a thin wall pipe 1 and the strength to withstand the impact of joining.