NOVELTY - A thermal decomposition gasifier has a carbonization furnace (1), a high temperature gasifier (2) and a high temperature modifier (3). Organic raw material is supplied to the furnace, carbonized, and supplied to the gasifier. A reformed gas is produced in the modifier by a specific method, and indirect heating of the furnace is carried out by the gasification gas, which is obtained by a specific method. The gas obtained after heating is used as product gas.    USE - Used for power generation equipment (claimed) for generating power, and for producing hydrogen gas used as fuel.    ADVANTAGE - The thermal decomposition gasifier enables the production of thermal decomposition gas having a reduced content of aromatic hydrocarbon. The processing capacity of plant organic substances is improved, and sensible heat is effectively utilized during the production of thermal decomposition gas. The heat energy released per unit volume of gasification gas is increased.    DETAILED DESCRIPTION - The thermal decomposition gasifier has a carbonization furnace (1), a high temperature gasifier (2) and a high temperature modifier (3). A raw material comprising plant organic substance is supplied to the furnace, and carbonized material generated in the furnace is supplied to the gasifier. The thermal decomposition gas generated in the furnace and high temperature gas containing oxygen are supplied to the modifier, and reacted to produce a reformed gas. The reformed gas is then supplied to the gasifier, and high temperature gas containing oxygen and carbonized material supplied to the gasifier are gasified. Indirect heating of the furnace is carried out by gasification gas, which is obtained by the gasification of carbonized material. The gas obtained after carrying out indirect heating is used as product gas.    An INDEPENDENT CLAIM is included for power generation equipment.    DESCRIPTION OF DRAWING(S) - The figure shows the power generation equipment.    Carbonization furnace (1)    High temperature gasifier (2)    High temperature modifier (3)    Gas turbine (4)    Hot water boiler (6)