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 including a gasket base material whose surface is at least partially provided with immobilized polymer chains, the gasket having a sliding surface provided with multiple annular projections, the annular projections including a first projection nearest to the top surface of the gasket, the first projection having a surface roughness Ra of 1.0 or less.
