Fourteen elderly people (mean age 73.8 years) kept a sleep log for 4–7 days, and their wrist-activity was monitored simultaneously. Their sleep onset and wake-up times, assessed by using actigraphy, were 21:04 and 05:51 hours, respectively, and these were advanced compared with young adults (00:45 and 07:34 hours, respectively). Elderly people often had naps actigraphically in the afternoon. There were marked discrepancies between the actigraphic sleep-wake state and sleep log in the afternoon and evening. Our observation implies that elderly people often have naps that are not subjectively recognized as naps. To rouse elderly people from a sleepy state, countermeasures such as improvement of the light environment and short-time naps are recommended.