A 58-year-old man visited our hospital with a chief complaint of epigastric pain. Computed tomography of the abdomen revealed a tumor in the left lobe of the liver accompanied by portal vein tumor thrombus, and Vp3 hepatocellular carcinoma was diagnosed. Prostate cancer with multiple bone metastases was also identified, and synchronous double cancer of the prostate and liver was diagnosed. The treatment strategy was to prioritize surgery for the hepatocellular carcinoma, for which curative resection was becomingnearly impossible. Left hepatic lobectomy was performed, and the postoperative course was favorable. Combined androgen blockade(CAB)with leuprorelin acetate and bicalutamide performed to treat the prostate cancer produced a significant decline in prostate-specific antigen(PSA)levels, causingthe metastatic bone lesions to disappear and relievingsymptoms. The patient has experienced no recurrence of hepatocellular carcinoma for 2 years 6 months since the initial treatment, and PSA levels have remained below the limits of detection. Few reports have described synchronous double cancer of the prostate and liver. In the present case, both cancers were advanced, but multimodal therapy combiningsurg ery(local treatment)and hormone therapy(systemic treatment)performed in accordance with the respective disease stages produced favorable results.