We herein report a case of muscle biopsy-proven microscopic polyangiitis (MPA) in a patient with tuberculosis. The patient had developed a persistent fever after the initiation of treatment for tuberculosis and was positive for myeloperoxidase-antineutrophil cytoplasmic antibody (ANCA). However, because conventional symptoms were lacking, determination of the biopsy site was difficult. Based on the findings of a biopsy of the biceps femoris, which confirmed small vessel vasculitis, the patient was diagnosed with MPA. The fever was alleviated by glucocorticoids. Tuberculosis and antituberculosis drugs can cause ANCA-associated vasculitis (AAV). A muscle biopsy is useful for the diagnosis of AAV.