The invention includes a step of supplying at least one heat control means of heating means and cooling means for conditioning the air temperature, and a step of manufacturing a fan for blowing air controlled by the heat control means, in which the step of manufacturing the fan includes a step of preparing a compound material having (i) glass fiber, and (ii) at least one copolymer of a copolymer produced from a monomer containing acrylonitrile and styrene, and a copolymer produced from styrene and a heat resistant monomer, a step of forming a molded part by molding the compound material, a step of assembling a fan by using the molded part, and a step of clearing the molded part of strain by annealing the fan by hot air circulation in a temperature range lower by about 5° C. to about 20° C. than the load deflection temperature, and in a wind velocity range of about 1 m/sec to about 3 m/sec. The fan having a load deflection temperature of about 100° C. or more by a testing method of JIS K 7207 at a load of 18.5 kgf/cm2. The air conditioner is manufactured in this manner. In this constitution, the required annealing time is shortened, and the productivity is enhanced. Moreover, the flowability of the compound material is heightened, so that the molding performance is improved.