This study examined the developmental feature of the self-actualization of infancy in a longitudinal study. One hundred one 6 years-old children were participated in this study. The preschool teachers accessed self-actualization tendency on each child twice a year and recorded their impressive episode. It was found that 70 percent of the children increased the score for self-actualization tendency. Although, as for the child whose self-actualization score was low at the 1st time raised the scores, the child whose score was high did not have a remarkable change. The improvement in a score was mainly found by the item of the contents about social development among 15 items which constitute a self-actualization measure. Also in preschool teachers, the child with a high self-actualization tendency had much episode about social adaptation, the child with a low self-actualization tendency did not. These facts suggests that there is individual difference of development speed in the dynamism that the self-actualization tendency improves, and social development is the core of development of the self-actualization of infancy.