The main purpose of this study was to examine the validity of quantitative data related to infant-nursery school teacher attachment. Firstly, qualitative data for 9 months were extracted from the same data which had once been sampled quantitatively. Secondly, the qualitative data and the quantitative data were compared. It seemed that infants went through the similar process in both data. That is, the infants began to show attachment behaviors toward their nursery school teachers and developed stable relationships with them. And the infants became to be able to control themselves, and to play with friends calmly. In conclusion, the validity of quantitative data for infant-nursery school teacher attachment was confirmed by comparing with qualitative data.