The sealing material is configured to be installed in a dovetail groove. The sealing material has a seal cross-section including a main body arranged on a bottom surface of the dovetail groove, and a lip portion which is bent from an end of the main body and extends toward an outside of the dovetail groove. The seal cross-section has such a V shape that each of the main body and the lip portion extends linearly from a bending position between the main body and the lip portion. A width B1 of the main body in a direction orthogonal to a direction in which the main body extends linearly is not more than a width B2 of the lip portion in a direction orthogonal to a direction in which the lip portion extends linearly. This configuration provides the sealing material which can be used under an extremely low load.