Boiler using waste plastic

A waste plastic boiler is provided to enhance the release rate of the fuel gas using the waste plastic and heat exchange rate capable of completely burning waste plastic residual which does not converted into fuel gas. A waste plastic boiler comprises a gas generation housing(110) having a hollow along its longitudinal direction; a transfer screw(130) which is installed to allow it to rotate inside the hollow; a drive motor(140) rotating the transfer screw; a gas generating device(100) consisting of a hopper(120) installed at one side of the housing so that the waste plastic is put into the transfer screw and a heater(160) installed on the housing in order to heat the fed waste plastic; a combustion housing(210) on which a pressure reducing part with its diameter directing toward the exhaust side tapered; and an air injection nozzle installed on the combustion housing in order to supply air to the combustion chamber.