As a surgical treatment of ulnar nerve entrapment syndrome includes simple decompression, medial epicondylectomy, and anterior transposition of the ulnar nerve into a subcutaneous or submuscular bed have been widely used. Despite many reports of these surgical procedure, there is little to guide the choice of one surgical technique. The purpose of our study is to analyse clinical and electrodiagnostic result after minimal invasive decompression by decompression and medial epicondyloplasty(deepening of ulnar groove). We have experienced 9 cases of ulnar nerve entrapment syndrome who were treated with decompression and medial epicondyloplasty. Male were five and female were four. The mean age at operation was 36 years ranging from 23 to 47 years. Operative procedure was to incise the medial intermuscular septum and aponeurotic arch of flexor carpiulnaris and to deepen the ulnar groove. Patients are allowed to do range of motion(ROM) exercise on the average 5days. All patient were relieved pain and improved motor and sensory function, and this procedure allows early ROM exercise after operation because the muscle have not been detached.