The present invention provides a gasket for glass or resin syringes which is laminated with an inert resin film and is excellent in plugging properties, liquid-tightness, and slidability. The gasket laminated with an inert resin film has multiple circular ribs that are to be in sliding contact with an inner wall of a syringe barrel, wherein the circular ribs include a front circular rib having a sliding contact portion whose cross section has a diameter that expands substantially linearly toward a back end of the syringe barrel, the linear portion has a length of 10 to 55% of the length of a sliding side face of the gasket, and the diameter of the linear portion which expands substantially linearly toward a back end of the syringe barrel has a diameter expansion ratio X between a minimum diameter r (mm) and a maximum diameter R (mm) of 0.1 to 8.0%.
