The present invention provides a new anti-tumor agent containing adiponectin as an active ingredient, particularly, an anti-tumor agent capable of inhibiting carcinogenesis in the liver, use of adiponectin as an anti-tumor agent, and a prophylactic or therapeutic method against a tumor using adiponectin. The administration form may be either oral administration, e.g., by tablets or parenteral administration, e.g., by injection； in the case of intravenous injection for inhibiting carcinogenesis in the liver, the dosage is 1 to 100 mg/kg/day per adult patient.
