This study was designed to evaluate the effects of an oriental medicine(Siryung-tang) on pain caused by Post-herpetic neuralgia. We treated a 70 year-old male patient who suffered left flank pain by Post-herpetic neuralgia. As for treatment, we used Siryung-tang. After seven-day of treatment, all symptoms started to improved. This study suggests that Siryung-tang is effective in treatment of pain by Post-herpetic neuralgia.