A gasket suitable for a syringe stopping with vacuum is provided. The gasket is compatible with sliding property within the sleeve and water-tightness of the syringe barrel after exiting the sleeve. The gasket includes a gasket body made of a liquid-resistant hard plastic having a tip surface contacting medicinal solution and a concave groove formed on a side surface facing an inner peripheral surface of a syringe barrel and formed continuously to the tip surface contacting medicinal solution； and a sliding contact ring made of an elastic material fitted in the concave groove. Then, an outer diameter D1 of a peripheral end of a tip portion including the tip surface contacting medicinal solution of the gasket body is set to be larger than the outer diameter D4 of the sliding contact ring.
