A case of angiomatoid malignant fibrous histiocytoma was presented. The tumor was unlike other variants of malignant fibrous histiocytoma because of prominent cystic change, haemorrhage and occurring in young adult. Our case was a 17-year-old boy who had been suffered from pyrexia and general fatigue. He was admitted to the medical ward in our hospital. The laboratory findings revealed only severe anemia, but the cause of pyrexia was not found. The patient was refered to us, orthopedists, with complainning of the soft part tumor of his right thigh. The pathologic examination by the biopsy showed malignant findings, then the tumor was removed widely with whole belly of the long adductor muscle.The tumor showed haemorrhagic cyst-like space with psuedocapsule macroscopically and the tumor was diagnosed microscopically as the angiomatoid malignant fibrous histiocytoma. His complaints and anemia were rapidly recovered after the operation. He has been followed for about five months, and no metastatic lesion and no local recurrence were found yet.