Behcet's disease is chronic and systemic inflammatory vasculitis, characterized by immunologically involving in variable size of arteries and veins. Clinically, principal manifestations are recurrent oral ulcer, genital ulcer, skin and eye lesions. Compared to other connective tissue disease, cancer is not accompanied commonly in Behcet's disease. But, immunological confusion such as T cell depletion or B cell hyperplasia, or long-term of immunosuppressive treatment lead to occurrence of malignancy. Recently, we experienced a case of maxillary mass, induced to abrupt headache in Behcet's disease, confirmed diffuse large B cell lymphoma by biopsy, and treated by rituximab-CHOP chemotherapy. Thus we report these with literature review.