For designing a comfortable visual environment, it is necessary to estimate adaptation luminance of the whole visual field with complicated luminance distribution. It is thought that such adaptation luminance is estimated by considering the summation of the adaptation luminance increase that is the effective luminance brought by a partial luminance of visual fields. For estimating the adaptation luminance, the additibity of adaptation luminance increase should be confirmed to the whole visual field.Under the various patterns of high luminance surfaces arrangement covering the whole visual field, the luminance difference threshold is determined to each subject for getting adaptation luminance. From the result of such subjective experiments, the additivity of adaptation luminance increase was confirmed in this paper.