A 68-year-old male visited our division with an elevation of PSA level. He underwent a needle biopsy of the prostate, and the histopathological diagnosis was poorly differentiated adenocarcinoma (Gleason score 4+3). The cancer was clinically diagnosed as T2aN0M0, and he underwent extraperitoneal laparoscopic radical prostatectomy and bilateral pelvic lymphadenectomy. Cystography 14 days after the operation still showed leakage at the vesico-urethral anastomosis and a dumbbell shaped bladder. A few days later, prominence of lower abdomen and a slight swelling of right leg presented with a high fever. Computed tomography revealed a giant lymphocele in the retroperitoneal space. We percutaneously punctured the lymphocele by using ultrasonography, inserted a pigtail catheter, and drained 1,000 ml of lymphatic fluid. After the puncture, sclerotherapy with minocycline was performed four times. Twenty days after the puncture, the lymphocele cavity was found to have shrunken and the pigtail catheter was removed. The lymphocele was diminished and did not recur thereafter.