A heat treating apparatus comprises a process chamber within which a wafer is subjected to a heat treatment. A supporting plate for supporting the wafer is arranged within the process chamber. A process gas is supplied from above into the process chamber. A main heating means for heating the wafer is arranged below the process chamber, with a transmitting window interposed therebetween. The main heating means includes a plurality of heating sources for irradiating the supporting plate with heat rays so as to heat the wafer indirectly and a rotatable table having the heating sources arranged on the front surface thereof. The heat treating apparatus also comprises an auxiliary heating means for compensating for an uneven temperature caused on the surface of the wafer by the main heating means. The heating source of the auxiliary heating means is arranged on the surface of the rotatable table together with the heating sources of the main heating means, and the heat output from the heating source of the auxiliary heating means can be controlled independently of the heat output from the heating sources of the main heating means.