The present invention provides a heat treatment system, which includes a treatment chamber having an input port and a discharge port for charging and discharging materials to be treated. A heating system including a plurality of pipe-like heaters positioned one after another in serial arrangement is provided so that the heating temperature is gradually increased for heating the steam or the atomized water introduced from the water feeding system into the heaters by applying voltage on the heaters to turn the steam and the atomized water to superheated steam, and for performing heat treatment on the materials to be treated by injecting the superheated steam into the treatment chamber. A circulating system is provided for sucking the superheated steam and the dry distillation gas in the treatment chamber and for supplying the steam and the gas again into the treatment chamber after deodorizing and filtering, and a control unit is provided for controlling operating conditions such as supply quantity of the steam, duration of treatment, etc.