In this study, we examined the effects of different plantar stimulus zones on body sway and lower limb muscle activity. A total of nine healthy male subjects stood on a plantar stimulator. Electromyography of the lower limbs and center of gravity were measured during plantar stimulation while standing. Plantar stimulation was conducted in 17 plantar zones and gradually increased in amplitude. Our results revealed that the condition of stimulating the heels shifted the center of gravity coordinate to forward compared with that of stimulating the forefoot. In addition, the amount of gastrocnemius muscle activity was remarkably higher in stimulating the heels than the forefoot. These changes increased with stimulation amplitude increment. The results of this study suggest that the effect of plantar stimulation is useful in fall prevention such as the development of insoles that improve body stability.