The effect of moisture content and temperature on the effective moisture diffusivity was investigated to identify the optimal drying condition for Japanese noodle (udon) by using a diffusion model. The drying of fresh udon with different moisture contents was carried out under constant conditions of relative humidity and airflow at 20°C, 30°C and 40°C. The effective moisture diffusivity calculated from diffusion model was found to be constant at each temperature, and not to be influenced by the initial moisture content of the fresh udon. The moisture content calculated from the effective moisture diffusivity (2.1-3.7×10(-7) cm(2) s(-1)) agrees well with the experimental data. The effect of temperature on the effective moisture diffusivity was adequately modeled by the Arrhenius relationship. The activation energy was 21.3 kJ mol(-1).