This study attempts to clarify the process of play transition in the forest and its environs. The play activity of children in kindergarten is constantly evolving alongside changes of the components of play, including activity (action or movement), roles, rules, and the physical environment (Sato, 2004). By observing children who were playing in nursery-rooms, playrooms, and playgrounds, Sato discovered that the scale of communications among children at play is wide. To clarify how play transitions to the forest, an observational study of children playing in the forest near their kindergarten was conducted. The results affirmed three forms of play transition: transition of place, transition of activity, and transition of both place and activity. By analyzing the circumstances of the three forms of play transition, it was found that discoveries and applications of the natural environment are related to the opportunities arising from play transition. Furthermore, the observations of transitions of both place and activity revealed that the transition of place itself is often seen by the children as a type of play activity. This may be related to both the much wider expanse offered by the forest and the ongoing communication between the children