The present invention provides a food/drink or pharmaceutical composition for oral administration for improving an acidic urine, comprising fucoidan or a fucoidan-containing material as an active ingredient, characterized in that a urinal pH is persistently increased; use of fucoidan or a fucoidan-containing material for production of the food/drink or the pharmaceutical composition for oral administration; and a method for improving an acidic urine by persistently increasing a urinal pH of a patient, which comprises orally administering fucoidan or a fucoidan-containing material to a patient.