To provide a spiral flow hot air drying furnace exclusively used for solid fuel (RDF) wherein high drying efficiency in safety at a low cost, and a dried matter of high quality are obtained.

This spiral flow hot air drying furnace exclusively used for solid fuel (RDF) uses the RDF as the fuel of a hot air generating furnace for sending the air to a rotary drying furnace installed on a frame, a spherical spiral flow converter is mounted in between the hot air generating furnace and the rotary drying furnace, and an ozone gas generated from an ozone generator is kept into contact with and mixed with the hot air when the hot air is converted into the spiral flow to eliminate dioxin. The spherical spiral flow converter connected to a rotary drying furnace connector with a changing port for charging the waste to be dried to the rotary drying furnace, a fly ash collector, an RDF combustion hot air generating furnace, and a dried matter collecting device connected to a terminal end of the rotary drying furnace, mounted on the upper part of the convertor, are included.