The subjects of this study are children belonging to a junior soccer club team which specializes in a single sporting event. We prepared an environment where G-balls could be used freely for a certain period and offered the subjects sporting programs. Our aim was to get fundamental knowledge on playing with G-balls through investigation of the inner reflection of the children and interviews with instructors. The result of the inner reflection investigation was as follows. The pleasantness was satisfactory with the score 4.8 out of 5 full points, in the first and the third trials in every class of the subjects. A tendency was observed through interview results with the instructors that the children in the class of elementary school enjoyed themselves by themselves at their free time, and students in the class of junior high school and high school utilized them for the purpose of training their body trunk or weight training. Furthermore, a tendency was also observed that the instructors comprehended the fundamental movement with G-balls as useful in the sense of body control.