Amusement was introduced for one month and interaction among the elderly and its influence on their physiological function and sleep were investigated. Methods: The subjects were 9 elderly females (age: 89.0 ± 4.7 years old) who periodically visited a day care service center for the elderly. The survey was performed between October 2015 and December 2015. For the amusement, Blackjack was introduced. The survey period was comprised of 3 amusement introduction periods: pre-amusement, and one week and one month after amusement introduction. In each period, the heart rate (HR), sympathetic nerve activity (CSI), and parasympathetic nerve activity (CVI) were measured during amusement, and the difference in the salivary amylase level between before and after amusement was determined. The sleep efficiency and sleeping hours were measured at night of the days with amusement. Repeated measures one-way ANOVA was performed regarding the survey period as a factor and HR, CSI, CVI, sleep efficiency, sleeping hours, and difference in the amylase level as dependent variables. Results: Significant amusement-induced changes were noted in the CVI and salivary amylase level. These were significantly lower at one month after amusement introduction than those in pre-amusement. Conclusion: Amusement-induced laughing and regret or interaction through the amusement influenced their autonomic nerve system and they may have felt comfortable.