NOVELTY - A waste material containing plastics (5) is thrown into a heating container (1), and a dropping lid (6) is placed on the thrown waste material. The waste material in the container is then thermally decomposed in anoxia or low oxygen state, and gas is generated. The gas generated during decomposition is absorbed and treated outside the heating container.    USE - For thermally decomposing general and medical waste materials containing plastics.    ADVANTAGE - The thermal decomposition apparatus has simple structure, and small size. The waste material containing plastics can be decomposed with high efficiency, after volume reduction and detoxification. The acidic solution can be neutralized efficiently without stirring. Maintenance of neutralization tank is easy.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following: (i) Thermal decomposition device of waste material containing plastics, which comprises a heating container into which a waste material containing plastics is thrown. A dropping lid is mounted on the waste material thrown into the heating container. A gas absorption opening (10) is provided in the heating container, through which a gas generated during decomposition is absorbed, and treated outside the heating container; (ii) Neutralization tank (20), which neutralizes an acidic gas condensate formed by condensation of gas generated during decomposition. The neutralization tank has an inclined division plate (22) with several holes, and an insoluble alkaline substance (23) deposited on the inclined division plate. An aqueous solution of acidic gas condensate is supplied from the downward portion of division plate, contacted with alkaline substance by passing through the holes of the plate, and neutralized. The neutralized water is then risen above the surface of alkaline substance.    DESCRIPTION OF DRAWING(S) - The figure shows the schematic diagram of thermal decomposition device of waste material containing plastics. (Drawing includes non-English language text).    Heating container (1)    Waste material containing plastics (5)    Dropping lid (6)    Gas absorption opening (10)    Neutralization tank (20)    Inclined division plate (22)    Alkaline substance (23)