We report the case of a 61-year-old man with pyoderma gangrenosum (PG) who was successfully treated with high-dose intravenous immunoglobulin (IVIg). He was transported to hospital with fever, pain and ulcer of the left inner thigh, and pancytopenia. PG associated with myelodysplastic syndrome was diagnosed, and treatment with methyl-prednisolone at 1.0 g/day for 3 days was followed by oral prednisolone. As the ulcer deteriorated when prednisolone dose was reduced, he was admitted to our hospital. IVIg was administered twice, with high fever promptly subsiding and the ulcer markedly decreasing in size. IVIg may represent a good option when steroid therapy proves insufficient.