The effect of hard layer due to thermal denaturation on the drying characteristics was examined experimentally and theoretically. The hot air drying of multi-layer sample, which consisted of Thermal ly Hardening Material (THM) and Thermally Stable Particle (TSP) layers, was performed. In the theoretical calculation, the formation of hard layer was expressed as the resistance to heat and mass transfers. The calculated results were compared with the experimental data. The period when the evaporation rate at the interface between THM and TSP layers governs the drying is observed, and the decrement degree of drying rate and the increment degree of sample temperature become small. During the period, the drying rate becomes lower as THM layer becomes thicker. In the case of relatively low temperature of drying gas, the effect of evaporation at the interface on drying rate becomes small. To obtain the short drying time, it is important that no THM layer exists near the surface.