PURPOSE: The titled inactivating agent forming insoluble compounds with phosphoric acid, polyphosphoric acid or salts thereof, preventing excess intake of phosphoric acid (phosphate), comprising a basic high polymer (salt) as an active ingredient.

CONSTITUTION: The aimed inactivating agent comprising one or more selected from a basic high polymer (e.g. protamine, salmine, clupeine, partially hydrolyzed chitin, chitosan, etc.) and/or salts thereof as an active ingredient.