Radiation measurement with film badges is influenced by thermal energy and it is sometimes reported to be exposed to higher radiation by mistake under the condition with higher temperature. Because of no practical data regarding relationship between temperature and radiation dose, estimation of the true value under the condition with higher temperature was difficult. The current study was performed to clarify the influence of probable high-temperature on the radiation dosimetry by film badge system. Serial measurements of temperature in the car confirmed that it can rise to 80°C or higher in the area irradiated with sun beam. The setting time was ranged from 3h to 48h and the temperatures were monitored from 60°C to 110°C. Exposure dose was increased by the elevation of temperature. Significant correlation was confirmed between the temperature and the exposure dose measured by film badges. It was also confirmed that high temperature influenced the sensitivity of film badges.