A 19-year-old male with diarrhea, abdominal pain, fever, and elevated C-reactive protein (CRP) levels was admitted to our hospital. Endoscopic examination and small intestinal contrast radiography revealed multiple longitudinal ulcers in the large intestine and ileum. A specimen biopsied from one of these ulcers revealed non-caseating epithelioid cell granuloma. He also had a draining anal fistula. Plain chest computed tomography (CT) and abdominal contrast-enhanced CT did not reveal any vascular abnormality. A diagnosis of Crohn's disease was made, and infliximab was administered. Following infliximab administration, the diarrhea and abdominal pain disappeared, longitudinal ulcers in the large intestine healed (as evidenced by endoscopic examination), and his anal lesion improved. However, fever and elevated CRP levels persisted. With the concomitant use of prednisolone, the fever and elevation of CRP levels eventually improved, and the patient was discharged. Both, however, recurred as the patient was weaned off prednisolone treatment; consequently, he was re-hospitalized. Contrast-enhanced CT upon re-admission revealed stenoses of the right renal artery, left common carotid artery, and left subclavian artery. In addition to Crohn's disease, the patient was diagnosed with co-existing Takayasu's arteritis.