This research is first to analyze an electomygram reaction of the lower limbs among the muscles used during a back-round kicking of Taekwondo, second to analyze the relationship between the muscles of the kicking limb and those of the supporting limb, third to compare EMG activity of expert with novice. Measured muscles are as follows; rectus fermoris which control flexion and stretching of femora and knee joints, vastus medialis and vastus lateralis, which control flexion and stretching of legs, and biceps fermoris, which control stretching of femora, bending of knee joints and abduction of the crus. The electomygram reaction of all these selected muscles were analyzed. Three kicks were performed, and electomygram of each of kicks were measured. Then, electomygram reaction of the best kick was used for electomygram analysis.