PURPOSE: To improve recognition performance for a substance having no heat source by calculating the luminance value of the substance, whose luminance is changed due to an environment, etc., in an infrared picture.

CONSTITUTION: In an objective luminance calculating part 5, based on the average and distribution of a temperature sent from a temperature sensor part 2 and the picture data luminance value sent from a memory 4, whether a high temperature area or a low temperature area is major in picture data is decided. In a data base 6, the relation between the temperature and the luminance value of the substance to be the detection object is stored, and the luminance value of the objective substance is calculated by the output of the temperature sensor part 2. To absorb the fluctuation of the gain of an infrared picture image pickup part 1, the luminance value is corrected with the use of the mean luminance value and distribution of the previously obtained whole picture data, the corrected value is sent to the picture memory 4 as the final objective detection luminance value, and the substance is recognized. Thus the substance having no heat source can be detected.