The present invention relates to a structure inside a chimney which includes an outer iron plate; a lining fastened and installed to the outer iron plate by a fastener; and insulation material charged and installed in a gap between the outer iron plate and the lining, thereby remarkably improving functionality of the structure inside a chimney and remarkably saving manufacturing costs, construction costs, maintenance and management costs, and the like by providing a nano inorganic coating layer at the inner side surface of the lining.
