NOVELTY - The body (21) has a thermoplastic resin film arranged between synthetic resin moldings i.e. valve body resin molding bodies (11, 12), where thickness of the thermoplastic resin film is 2 mm or less. Conductor powder is mixed in the thermoplastic resin film. Thrust is applied between the synthetic resin moldings. A metal thin film is coated in the thermoplastic resin film. A metal foil is positioned between the synthetic resin moldings, where thickness of the metal foil is 0.5 mm or less. Dielectric heating of the thermoplastic resin film or the metal foil is carried out by microwave.    USE - Microwave heat generating body for welding resin-made valve bodies of an automatic-transmission car. Can also be used for an intake manifold, a reservoir tank and a valve body of a motor vehicle, hydraulic control fixing multilayer resin components, a separator of a fuel cell and a thermoplastic resins member manufacturing field.    ADVANTAGE - The thermoplastic resin film is arranged between the synthetic resin moldings, the thrust is applied between the synthetic resin moldings, and the microwave heat generating body is welded by heat that is generated by the microwave, so that heat-emission-temperature degree can be controlled highly and uniformly, thus ensuring stable welding and manufacturing the resin-made valve body easily. The body enables eliminating a process of waste cutting and simplifying cleaning, so that productivity of the resin-made valve body is improved. The thrust is applied to a joining direction that joins the synthetic resin moldings, so that finishing precision of the synthetic resin moldings can be raised. The thermal capacity of the body is small, so that mass production can be ensured in a short time.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for welding a microwave heat generating body between resin-made moldings.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a resin-made valve body. '(Drawing includes non-English language text)'    Linear solenoid valve (A)    Valve body resin molding bodies (11, 12)    Microwave heat generating body (21)