The present invention provides a gasket (2) excellent in properties such as sliding properties and resistance to liquid leakage. The present invention relates to a gasket including a gasket base material (1) whose surface is at least partially provided with immobilized polymer chains (21), the gasket having a sliding surface (14) provided with multiple annular projections (14a, 14b, 14c), the annular projections including a first projection (14a) nearest to the top surface (12) of the gasket, the first projection having a surface roughness Ra of 1.0 or less.
