A sealing material for dovetail groove having an excellent sealing function in which biting, rolling and twisting are not likely to occur. Cross section of the sealing material (10) for dovetail groove made of an elastic material has a flat bottom side (12) located on the bottom face of a dovetail groove (22), left and right oblique sides (14) rising obliquely outward from the opposite sides of the bottom side (12), left and right stretching shoulder parts (16) located in the dovetail groove (22) closely to the opening thereof at the forward end of the left and right oblique sides (14), a protrusion (18) provided in the center of the left and right stretching shoulder parts (16) and projecting above the opening of the dovetail groove (22), and recesses (17) provided between the stretching shoulder parts (16) and the central protrusion (18) and recessed inward of the tangential line to the stretching shoulder parts (16) and the central protrusion (18).
