Dynamic posture of sports activity is one of the most important aspects to evaluate the player’s skill. Such sports that need evaluation from the objective observation like figure skating and skiing have difficulty in evaluation of skill. The conventional training method for such sports was the feedback of subjective comments from the experts regarding the performance. To overcome this problem, this paper focuses on developing a new training system to give a clear guide for body balance control to the athlete. The system gives scores and messages for raising up the performance skills. It causes improvement of the dynamic posture. This paper introduces a scoring system focusing on the ski’s parallel turn. The system automatically scores skill for body balance control regarding three aspects: the tempo at turns of body balance changes between the right and the left, the distribution of body balance, and the angle between the snow slope and the body of the skier. The system has been impl emented in an Android smartphone and evaluated the effects of the scoring functions from the three aspects applying to a middle level skier.