We investigated whether exposure to the odor of extracted cedar essence (CE) has (i) an influence on spontaneous activity and sleep-wake states of rats and (ii) a sleep-promoting effect on human daytime nap after taking an ordinary night's sleep. In rats exposed to CE, spontaneous activities and amount of wake were significantly decreased, while the amount of non-rapid eye movement (NREM) sleep was significantly increased. In human daytime nap, NREM sleep stage 2 latency was significantly shortened after exposure to CE.