Abstract: The present invention relates to a sealing material for hydraulic fitting flanges, in more particular, a sealing material which is configured in a specific shape, departing from the shape of traditional O-rings, to prevent it from being separated from fitting flange, improve assembly work efficiency, eliminating the necessity of extra work step(s) for maintaining it at the intended position, and provide it with excellent sealing and retaining performance. To achieve the above mentioned objects, the sealing material, in compliance with the invention in a torus shape, placed in the sealing material groove of fitting is characterized by its inner diameter side or outer diameter side being formed in the shape to match with, or to be in contact with the corresponding face of the sealing material groove, and the lateral sides connecting the inner and outer diameter surfaces are formed with protruded areas.