The present invention provides a gasket excellent in properties such as sliding properties and resistance to liquid leakage. The present invention relates to a gasket having at least two annular projections and at least one annular valley on its sliding surface, the sliding surface being at least partially provided with immobilized polymer chains, the annular projections including a first projection nearest to the top surface and any other projection, the outer diameters of the other projection and the annular valley being in the range of 94 to 98% and 85 to 92%, respectively, with respect to the outer diameter of the first projection taken as 100%.
