ln this study, the measurement of the speed of the hit ball by the speed radar gun and the motion picture camera measurement were executed. As a result, it was clear that the speed radar gun was able to accurately measure the speed of the hit ball. Moreover, the ball speed by use of the metal baseball bat was significantly faster than the ball speed by use of the bamboo bat. In order to predict the one’s baseball aptitude on the basis of the speed of the hit ball, discriminant analysis was applied by using the data of 69 baseball players of senior high school. The investigation of the validity of the obtained formula, z = 0.158×(ball Speed)－0.056×(height)－11.018, demonstrated that the baseball players’ aptitude was able to be predicted at 70 percent level of precision using the data of the speed of the hit ball and height of the subject.