The surgical treatment of large, deep defects on the midline of the lower back or lumbar area comprises difficult reconstructive challenges. Various flaps have been designed to reconstruct the defect area. We herein report a 70-year-old Japanese woman with a large, deep ulcer in the midline of the lower back, caused by postoperative radiation therapy for eccrine porocarcinoma. The ulcer was successfully treated with surgical debridement followed by reverse latissimus dorsi musculocutaneous flap. This flap is reliable and useful for reconstruction of a large, deep midline defect of the lower back, having large and bulky tissue with a sufficient blood supply.