Cold air drying was conducted on steamed chestnut-sweet potato to improve its quality, convenience, and preference as snack. Steamed sweet potato was dried from 10 to $25^{circ}C$ for 48 hours, and moisture contents, colors, texture, and taste were evaluated. The lowest moisture content was 4.53% at $25^{circ}C$. Lightness decreased while other color values (a, b, and ${Delta}$E) increased with increasing drying temperature and drying time. Reducing sugar and soluble solid contents ranged from 93.22~190.35 mg/g and 17~60 $^{circ}Brix$, respectively. The highest hardness of chestnut-sweet potato was 25.13 kgf/$cm^2$, and springiness and cohesiveness were 88.60, and 94.87%, respectively, when dried at $25^{circ}C$ for 48 hours. Sensory evaluation score was highest at $20^{circ}C$ for 24 hours. The optimum drying conditions were determined to be $19^{circ}C$ and 39.5 hours by RSM(response surface methodology).