A 37-year-old Japanese man was diagnosed with liver cirrhosis due to Wilson's disease in 2001 and treated with D-penicillamine. Thereafter, he was admitted to our hospital for further examination of a space occupying lesion in the liver. The patient was diagnosed with hepatocellular carcinoma (HCC) (7th segment, 2.5 cm in diameter) in May 2010 and treated with radiofrequency ablation therapy. Biopsy findings from a non-cancerous area revealed a fatty liver, though cirrhotic nodules were not found. Long-term treatment for Wilson's disease may improve hepatic fibrosis, and careful screening for HCC by abdominal imaging is needed in such cases.