To provide a heating apparatus of low cost which can quickly and effectively heat a process gas while controlling a rising of an exhaust conductance, and to provide a process-gas treatment system which heats the process gas to a high temperature using the heating apparatus and maintains the process gas at the high temperature over a long distance of the lower stream.

A hole part 221 of a plurality of fins 220, arranged in a heating passage part 200 of the heating apparatus 1, is arranged so that the process gas flows while being spirally introduced. The process gas, which passes the hole part 221 to be changed to a spiral state, is heated by a heat radiated from a cylinder 210 and the fins 220 so that a temperature preventing a reaction byproduct from adhering is maintained to the last end of a discharge passage of the lower stream.