The purpose of this study was to identify whether preschoolers and teachers showed interventions which were related to sincere apology. 4-year-old children and 6-year-old children were observed in free play situations. First, it was found that the teacher intervened to conflicts more than preschoolers in the 4-year-old conflict situations, though 6-year-old children intervened more than the teacher to other children's conflict. Then, it was indicated that the teacher of both 4-year-old class and 6-year-old class showed interventions which were related to sincere apology, because they showed all the three interventions (ascertainment of the fact, ascertainment of the feeling, and speaking for another) leading to reception of responsibility and feeling guilty which were necessary for sincere apology. 6-year-old children also showed all the three interventions which were related to sincere apology, although 4-year-old children showed only one of them, ascertainment of the fact. Additionally, there was a possibility that they model after teachers' interventions. Then, it was found that teachers showed interventions which were related to sincere apology to not only 6-year-old children but also 4-year-old children for whom it was difficult to apologize sincerely. And it was also found that it was until 6 year old that preschooler showed intervention related to sincere apology.