A thermal treatment apparatus and method of thermal treatment are provided wherein the apparatus includes a treatment chamber used to thermally treat an object material held therein, fluid passages formed so as to extend along an outer surface of the treatment chamber, a heating means for the thermal treatment operation placed in the fluid passages, a fluid passing means for passing a fluid through the fluid passages while bringing the fluid into contact with heating surfaces of the heating means, and a control means for controlling the temperature and flow rate of the fluid passing through the fluid passages in at least one period of time during the thermal treatment operation, the fluid passing means further includes a plurality of blast rate variable fans arranged in parallel with the fluid passage and having mutually different flow rates.