Provided are a sweetness and/or saltiness enhancing agent and a method for enhancing sweetness and/or saltiness. This sweetness and/or saltiness enhancing agent includes, as an active ingredient, an oxidized oil or fat that has a peroxide value of 15 to 180 and contains 10 to 100 mass% of milk fat. This method for enhancing sweetness and/or saltiness of a food product is characterized by adding to a food product an oxidized oil or fat that has a peroxide value of 15 to 180 and contains 10 to 100 mass% of milk fat.