This study aims to investigate teachers' aids and environmental composition to make four-year-old children foster "an ability of interacting with others" through exchange activities with three-year-old children. This study employed recorded episodes of the exchange activities and teachers' conferences, and demonstrated teacher's better support and environmental composition to foster four-year-old children's ability to interact with others. The results show that the following four aids and environmental compositions are important to foster the ability of interacting with others: (1) teachers' involvement to accept the children' sentiments: (2) teachers' aids to secure plenty of time and place for the children to play at their own pace when they want to: (3) teachers' address to prompt children's' confidence: (4) teachers' address to admire what the children come into contact with in their own way.