A microcomputer drying system, which could be designed to be operated easily and economically, was developed. The optimum drying conditions with this system for onion and ginger were obtained. The temperature. relative humidity, and weight of material were measured and controlled successfully, and the better quality of products was obtained. Optimum drying condition for onion was 65℃ and 25% RH, and for ginger was 50℃ and 25%, respectively.