Recently, established transportation system is actively done to the research on ITS that starts achieving a more excellent traffic environment by using most-advanced information and communications technology. We studied the method of evaluating physiologycal state of human based on facial skin thermal image analysis. However it is said that facial skin thermogram have a susceptibility to environmental variation. In this paper, how much the facial skin thermogram effected the influence of the outside environment was examined. As a result, when there is no stressor from the outside, the environmental variation can be removed by calculating the temperature of ( nasal - forehead ). On the other hand, in the case of giving subject the stressor, the change of temperature appeared only nose.