Information of sleep stage was one of the most important clues for sleep quality. The purpose of this study was to measure the effects of mattress types on sleep quality, the skin temperature and to estimate the subjective rating. The hypothesis was tested whether sleep quality was different when subjects slept on mattress suitable for the bodily shape or not. Polysomnography is basically the recording of sleep. The several channels of brain waves (EEG), eyes (EOG), chin movements (EMG) and heart (ECG) were monitored. Six subjects spent 6 days and nights in the laboratory and the data of sleeping 7h for each of 3 nights was analyzed. Mean skin temperature, deep sleep (III and IV), sleep efficiency, sleep latency and subjective ratings were significantly affected with mattress types. When subjects slept in comfortable beds, mean skin temperature was higher than that of uncomfortable bed. Their skin temperature of the lower body, sleep efficiency and the percentage of deep sleep were higher, too. The percentage of wake after sleep onset was lower when subject slept in a comfortable bed.