A 57-year-old woman was admitted due to a hemorrhage from esophageal varices. Laboratory tests showed liver dysfunction, elevated immunoglobulin G levels and positivity for anti-nuclear antibodies. Serum hepatitis B virus and hepatitis C virus markers were negative. The liver biopsy specimen was compatible with autoimmune hepatitis, and low-dose prednisolone was started. During the follow-up, her serum alanine aminotransferase levels continued to fluctuate between 40 and 60 IU/l. Nine years later, hepatocellular carcinoma 20 mm in diameter was detected. This case suggests that hepatocellular carcinoma develops even if serum alanine aminotransferase levels are maintained at less than twice the upper normal limit.