An anti-biofouling method which suppresses biofouling in water includes a preparation step (S10) of using a copper alloy-made anti-biofouling object member immersed in the water as a cathode electrode, and immersing and arranging an anode electrode member serving as a counter electrode of the anti-biofouling object member in the water, and a current supplying step (S12) of supplying DC current between the anti-biofouling object member and the anode electrode member.