The purpose of this study is to clarify the process by which preschoolers acquire knowledge of daily work.“Clean-up” scenes were focused on and analyzed in order to establish how this knowledge is acquired. The subjects were 30 three-year old and 28 four-year old preschoolers. They were observed for one semester,from April to July, and were analyzed from the point of view of group formation. The teachers involved with these classes were interviewed about clean up activities and preschoolers.The four-year old preschoolers were more involved in cleaning up than the three-year olds. They did it more frequently, and in addition, they volunteered to clean up more than the three year-olds. However, in the early stages of the semester, neither the four-year old group nor the three-year old group volunteered to clean up, but later in the semester they did. This was identified as the process by which preschoolers adapted to their class.These results showed that the acquisition process of daily work in the kindergarten was explained by both the factors of development and group formation.