The exchange activity of the infant and the senior citizen was emphasized in "Welfare vision of the 21st century" that had been published in 1994 in Japan. After that, the effect of the exchange activity was executed without being confirmed. Then, it was tried to clarify the effect of the exchange activity of the infant and the senior citizen in research. The investigation was done in the Shimokamagari compound welfare facilities. The method is observation of the exchange activity, questions parents of the infant, and is a questionnaire to the senior citizen. Consequently, it has been understood that the infant affirmatively experiences the exchange activity, and has acquired sympathy and high communications skill. And, it has been understood to speak the exchange with the senior citizen to the family happily. The subjective well-being inventory was investigated about the senior citizen. There was for better or worse no result the subjective wellbeing inventory of the senior citizen. As for the exchange activity of the infant and the senior citizen, the infant's having the positive influence became clear, and the tendency to the positive influence became clear from the result of this research for the senior citizen
