A 67-year-old woman was admitted to our hospital, because of wasting of the thigh muscles. Muscular atrophy was confined to the thigh muscles, suggesting that she had quadriceps myopathy. Muscle biopsy from quadriceps muscle revealed characteristic findings, such as invasion of the endomysium and muscle fibers by inflammatory cells, the presence of rimmed vacuoles and ragged red fibers; thereby, she was diagnosed as having inclusion body myositis (IBM). Based on elevated titers of autoantibody as well as biopsy findings from salivary gland and liver, she was also diagnosed as having chronic thyroiditis, Sjögren's syndrome and autoimmune cholangitis. Currently, the pathogenic mechanism underlying IBM is not clarified, however, various factors have been suggested to contribute to it, such as viral infection or mitochondrial insufficiency. Although the pathogenic backgrounds underlying IBM are likely heterogeneous, an autoimmune-mediated mechanism may be related to the pathogenesis of IBM in the present patient.