The education process of gross motor skills in elementary schools consists of guidance, execution, and evaluation.  The evaluation process, however, tends to put much less efforts (only by looking, typically speaking) compared with others because the teachers cannot spare enough time and power for that after guidance and execution.  We exploit a motion capture system that is capable of analyzing video in real time only by taking children using USB camera that connects to a laptop PC.  It does not require any attachments to the children or any limitation in their motions, and it enables quantitative evaluation of motor skills and further analyses such as the statistical comparison nationwide in future.  On the other hand, gross motor skills are evaluated with respect to the criteria standardized in the Test of Gross Motor Skills (TGMD) that has been used widely all over the world.  The proposed method automatically quantifies the positions and the angles of interesting body joints and the timing of each motion that can be directly used for TGMD-based evaluation.  This presentation shows the results of several comparative studies conducted for the evaluation of gross motor skills of children using the proposed method.