Purpose : The purpose of this study was to assess the effectiveness of Extracorporea Shock-wave therapy(ESWT) on the pain and improvement of wrist extensor strength which is one of the available medical treatment in patients with lateral epicondylitis. Object and Methods : The subjects of this study were consisted of 15 patients with lateral epicondylitis, These medical treatments was conducted total 6 time for 3 weeks. In the ESWT application group. To investigate the effectiveness of the treatment after ESWT treatment, Pain was measured by visual analogue scale(VAS) which is divided into 10 ranks and wrist extensor strength was measured by Aneroid phygmomanometer Results : 1. It was showed that VAS and wrist extensor strength before treatment and after two treatment(1 week) were no significant differences(p<0.05). 2. It was showed that VAS and wrist extensor strength before treatment and after four treatment(2 week) were significant differences(p<0.05). 3. It was showed that VAS and wrist extensor strength before treatment and after six treatment(3 week) were significant differences(p<0.05). Conclusion : We think that ESWT for the patients with lateral epicondylitis. is effective to wrist extensor strength and decrease of pain.