A gasket (1) for use in a syringe has a core part (2) and a coating layer (3) formed on the core part (2) at least a portion thereof which contacts the syringe. In a portion where the coating layer is formed, an outer surface of the core part (2) is not exposed, and an outer surface layer of the core part (2) is formed of the coating layer (3). The coating layer (3) is an elastic solidified material layer made of a silicone-based resin composition. In an enlarged image of the coating layer (3) observed in an axial section of the gasket by using a transmission electron microscope, the coating layer has island-shaped solidified parts and sea-like solidified parts each positioned between the island-shaped solidified parts and linking the island-shaped solidified parts to each other and does not substantially have pin holes. The island-shaped solidified part is composed mainly of aggregates of reactive silicone.
