An oil deterioration suppressing apparatus is provided. The apparatus may include a filtering portion including a filter element for filtering oil, and a deterioration suppressing portion including a powdery deterioration retarder which suppresses deterioration of oil. The deterioration suppressing portion may include a flow passage wall which holds the powdery deterioration retarder and defines an oil flow passage, and the powdery deterioration retarder includes mesoporous inorganic material.