The authors investigated the condition of self-physique perception and eating behavior, and the relationship between self-physique perception and eating behavior of high school students in Japan. Regarding self-physique perception, subjects were shown six pictures of physiques and asked to choose one physique each for their actual physique and their ideal physique. With respect to eating behavior, the Japanese version of the Eating Attitudes Test (EAT)-26 was used. Groups of underweight girls, normal girls, and normal boys tended to regard their actual physiques as rather broad, demonstrating that many girls are excessively preoccupied with thinness. The rate of eating problems was 11.2% for the girls and 2.4% for the boys. For both boys and girls, those who idealized the thinner physique scored higher in terms of the EAT score and factor I score. Education regarding body perception and diet must be undertaken as soon as possible in Japan.