Various robots had been developed lately, not only for industrial use but for home use too. In our previous study, we had developed a playmate robot system that is designed to play with children. Child personality observation is important during play situations for smooth interaction, in order to sustain the child's interest. Therefore, we considered that the robot system should be able to distinguish children's personality types or tendencies. As a result, the relationship between the child's personality test score and head movement observed during the robot play interaction was found to be significant. This suggests the possibility of an adaptive robot system that plays with children in accordance to each child personality.