This study aims to find out the effect of swimming program on elementary school bodies’ body composition(weight, %body fat and BMI) and health physical fitness(Cardiovascular endurance, Muscular strength, Muscular endurance, Flexibility) for 12 weeks. The study was performed on 27 elementary school student in 2 different groups - 13 in swimming practice, 14 in non-motion. The results were the followings: 12-week of swimming program had significantly reduced body fat percentage. Therefore it had positive effects on body composition. Additionally, it had improved on cardiovascular endurance, muscular strength and muscular endurance on health physical fitness. It is thought to be due to constant contractions and relaxations of the muscles through regular exercises, which enhanced burning off fat and muscular strength so influenced positive effects on physical ability. It is necessary to have exercise habits to maintain the health, but also to improve life habits.