PURPOSE: To prevent a hazard that a combustion chamber comes to an unusual temperature, by providing a water circulation duct in a combustion chamber of a combustion part made by forming a hollow part within a water tank, in a device wherein hot water is obtained by burning gas generating within a gasification device.

CONSTITUTION: A water tank 4 is formed to a hollow structure, through which a combustion chamber 3 is constituted, in a boiler provided with the water tank 4 on the upper part of a gasification device (as outlined in a sketch) of a waste tire to be installed on a foundation part. Then, a water circulation duct 5 is made to form within the combustion chamber 3 in such a form that a natural convection of hot water is not disturbed. That is, cylindrical heat absorption components 7 and 8 are arranged in about the center of the combustion chamber 3 in two steps form, both the heat absorption components 7 and 8 are connected by a duct 9 with each other, the lower heat absorption component 8 and the bottom of the tank 4 are connected by ducts 10 and 10 with each other and the upper heat absorption board 7 and the upper part of the tank 4 are connected by slant ducts 11 and 11 with each other. Then, about two thirds of the combustion chamber 3 and its bottom shall be covered with a heat insulator.