We describe a case of a 69-year-old woman who developed rapidly progressive hepatocellular carcinoma (HCC) associated with autoimmune hepatitis (AIH) after a 7-year follow-up. Markers for viral hepatitis were negative. Serum tumor markers including alpha-fetoprotein and prothrombin induced by vitamin K absence II rose suddenly, and a large tumor was detected in spite of regular surveillance for HCC. Surgical treatment was performed. The resected liver specimen revealed well to moderately differentiated HCC. Ki67 staining showed rapid proliferation of the HCC. Although the incidence of HCC in patients with AIH has been unclarified, the possible complication by HCC must not be overlooked.