The purpose of this study is to verify the effect of the practical guidance for kindergartners, using a fresh tomato, to improve their unbalanced diet. The guidance consists of explaining importance of diet and reading a picture- story show featuring a tomato. To verify the effect, I made researches, before and after the guidance, on change of children's eating habit of a tomato. First of all, we divided children into the three age groups, and compared each group with the other two respectively. There were significant differences shown between the youngest group and other ones. We found that the youngest children ate least tomato and girls ate more tomato than boys in any age group, however, there was no significant difference between the eldest and the middle groups. After the guidance was given, their eating habit of a tomato improved significantly. The guidance raised children's interest in a tomato and improved their distaste to it. This guidance was especially effective for the children in the youngest group.