Objectives : As obese children have been increased, the interest in the impact of obesity on growth also have been increased. This study is to examine relations between obesity and skeletal maturity by analyzing body compositions and bone age. Methods : Subjects were composed of 233 children from 6 years to 17 years of age, without any other diseases related to growth, who visited the department of pediatrics, OO oriental medicine hospital and measured their body composition (body mass index, body fat ratio, fitness score) and bone age. Results : 1. As body mass index was increased, the skeletal maturity significantly was also increased. 2. As the mean of bone maturity was increased, the BMI was increased from the underweight type to the normal type to the overweight type; the bone maturity was increased as the fat ratio was increased from the normal type to the obese type to the excessively obese type; and the bone maturity was higher in the weak, obese type than the normal type when classified according to the Fitness Score. 3. The bone maturity of the overweight group in the BMI classification and excessively obese group in the fat ratio classification significantly were increased. 4. Skeletal maturity significantly was increased in children who developed secondary sexual character. 5. The significance of obesity causing increase of the skeletal maturity was higher in boys than in girls. 6. Only in the case of children without development of secondary sexual character, obesity caused an significant increases in the skeletal maturity. Conclusions : Obesity could cause the increase of skeletal maturity, and the obesity could affect more to the boys than girls and more to the children than teenagers.