Purpose : The purpose of this study was to examine immediate effects of 15 minutes plantarflexor static stretching in quite stance. Methods : Twenty-nine subjects were measured static balance during 1 minute in quite stance with eye closed condition before and after 15 minutes plantarflexor static stretching. Static stretching range was limited from $15^{circ}$ to $20^{circ}$ dorsiflexion within comfortable range. Results : The result of this study showed that postural sway significantly increased during 1 minute quiet stance after 15 minutes static stretching(p<.05). Before stretching, postural sway significantly decreased during 41-60 seconds compared to 0-20, 21-40 seconds(p<.05). After stretching, postural sway was decreased significantly over time 0-20, 21-40, and 41-60 seconds(p<.05). Conclusion : The prolong plantarflexor static stretching may require biomechanical, neurological adaptations prior to walking or sport activities for safety.