Disclosed is a method for producing a double-crosslinked hyaluronate material. A hyaluronic acid or a salt thereof is sequentially reacted with an epoxide compound and a carbodiimide compound to produce a more biodegradation-resistant hyaluronate material. The HA acid is preferably reacted with the carbodiimide first, and more preferably in a mixed solvent including water and an organic solvent, such as ketone.