PURPOSE: To facilitate sufficient ensurance of airtightness of an incinerator, to relieve the burden of a worker, and to shorten a term of construction at a site.

CONSTITUTION: A lower incinerator body constituting element 20a a stoker 21, an ash chute 24, and an ash discharge passage are integrally assembled in a support frame constituting element 70a. A lower unit 80a having a joint extending approximately along a horizontal direction is formed on an upper surface and fixed to a base, formed in a flat shape, through a lower support frame constituting element 70a. Further, an intermediate part incinerator body constituting element 20b and a topmost part incinerator body constituting element 20c are integrally assembled in support frame constituting elements 70b and 70c and joined with a lower incinerator body constituting element 20a to build an incinerator 20 by means of incinerator body constituting elements 20b and 20c. By joining the elements 20b and 20b with a lower support frame constituting element, the support frame constituting elements have respective intermediate part unit 80b and topmost part unit 80c by means of which support frame bodies to support the incinerator 20 to a base are built.