Purpose This study investigates the effects of extracorporeal shock wave treatment on the muscle tone and static stability of gastrocnemius muscle according to the energy amount in adolescent with spastic cerebral palsy. Methods The low energy group(n=9) and high energy group(n=9) to which extracorporeal shock wave was applied were randomly selected. The muscle tones of all subjects were measured before intervention, immediately after intervention, and 5 min after intervention. The static stability was measured before intervention and 10 min after intervention. Results Muscle tone significantly decreased both in the group to which high energy extracorporeal shock wave was applied and the group to which low energy extracorporeal shock wave was applied. Muscle stiffness statistically significantly decreased only in the group to which high energy extracorporeal shock wave was applied (p<.05). The difference in the amount of change between the two groups was statistically significant only before intervention and immediately after intervention (p<.05). Furthermore, regarding static balance, the sway area measured with eyes open showed a statistically significant difference between the two groups (p<.01). The sway path length showed a statistically significant decrease 10 min after intervention only in the group to which high energy extracorporeal shock wave was applied. Thus, the intergroup change in sway path length showed a statistically significant difference (p<.01). Conclusion This result suggests that extracorporeal shock wave using a high energy is more effective than extracorporeal shock wave using low energy in the reduction of muscle tone in adolescent with spastic cerebral palsy.