Abstract: The invention relates to a method capable of enhancing both the antifouling properties of a high entropy alloy and also the mechanical properties thereof, without using chemical substances such as antifouling paints to prevent the attachment of animals and plants such as barnacles, mussels, sea lettuces, diatoms, etc., the method according to the invention being characterized by the use of severe plastic deformation to reduce the grain size in a high entropy alloy and thereby impart to the high entropy alloy a property of suppressing the attachment of aquatic or marine organisms, and according to the method, environmental issues caused by the use of antifouling paint, which is conventionally the most widely used method, may be resolved, and the energy efficiency of ships may be improved, thereby reducing societal and economic loss.