Mental processes of twelve subjects who underwent thee days of sensory restriction were analyzed upon their self-reports and behaviors emitted during the experiment. Five categories of subject's reaction to the environment of sensory restriction, thinking and fantasy, perceptual experience, emotional state, emitted behavior and posture, and alpha frequencies of EEG, could be better information to estimate the degree of subject's mental deterioration. In order to search the critical point of tolerance for sensory restriction, three types of reaction style, emotion expression, regression-stability and reality coping, were classified. It was suggested that occurrence of impulsive emotion for emotion expression style, recollection of child days in a half-day long for regression-stability style and strong expression of unplesant emotion for reality coping style might be critical for sensory restriction.