To provide a combustion device to completely decompose dioxin generated due to combustion of RDF(refure derived fuel), minimize dropping of an RDF component to a furnace bottom, and besides perform uniform combustion of the RDF.

By using a combustion device formed such that mixture fluid of fuel and air is fed to a burner 4 and combustion air to completely burn incomplete combustion gas of fuel by the burner 4 is charged through an air charge port 13 for two-stage combustion, crushed RDF(refure derived fuel) is fed to an air charge port 13 for two-stage combustion by air 26 for conveyance. Since the RDF charged in a furnace 5 through the air charge port 13 is burnt at a combustion temperature high enough to decompose dioxin, no dioxin is discharged to the outside of a system. Since the height level of the air charge port 13 is a region where the ascending flow speed of combustion gas in the furnace 5 is highest, a ratio of the crushed RDF falling on a furnace bottom is decreased to the minimum.