An extended temperature-change method was proposed for calculation of moisture mass history or drying rate curve from temperature history during the infrared drying process. The authors had previously proposed the temperature-change method for acquiring the drying rate curve during hot-air drying, in place of the common mass-change method. Experiments of infrared drying and hot-air drying were performed using a thermocouple and a radiation thermometer for temperature measurement, and temperature and moisture mass histories were obtained. In the previous studies of hot-air drying, temperature of coating surface was measured with a radiation thermometer. In this study, a modified measurement technique was proposed in which temperature on the backside of the coating base was measured with the radiation thermometer. The temperatures of the two thermometers showed good agreement. Moisture mass histories for infrared drying were calculated by the extended temperature-change method from the temperature histories measured with the two thermometers. The calculated mass histories showed good agreement with each other and with the measured mass history, suggesting the validity of the extended method with the radiation thermometer. It was noted that the extended method gives an approximate curve of drying rate for hot-air drying.