Pyoderma gangrenosum (PG) is a destructive inflammatory disease characterized by painful ulcerative lesions with neutrophilic infiltration in the dermis. The etiology and pathogenesis of PG are poorly understood. Although approximately 50% of the cases on PG have been described in association with inflammatory bowel disease and other hematologic diseases, a few rare cases of PG have indicated ulcer development initiated only after minor trauma and ischemic condition. A 66-year-old man referred to our clinic presenting multiple painful ulcers on the both lower legs which had been relapsed for past 4 years. Pitting edema and surrounding brownish reticular pigmented patch were also found. He received total knee replacement surgery a year before those ulcers occurred. Before being referred to our clinic, he was diagnosed as venous leg ulcer by these clinical features and prior history of surgery. In spite of prolonged treatments for venous leg ulcers, the lesions had not been improved. Through the skin biopsy, PG was diagnosed and systemic corticosteroid treatment was added to the ongoing conventional treatment for venous leg ulcers. The recalcitrant ulcers responded well and showed a dramatic improvement. Here, we report an atypical case of PG on the site of venous insufficiency leading to an inevitable misdiagnosis as venous ulcers.