A gasket device is for use in a pre-filled syringe having a cylinder (11) for containing liquid drug (LM) in sealing tightness. The liquid drug is pressurized by moving a plunger (14) in the cylinder. The gasket device includes a gasket body (21, 51), having resiliency, and movable toward the liquid drug with a front end (14a) of the plunger. A laminate layer (22, 52) is formed from PTFE (polytetrafluoroethylene), and disposed to cover a surface of the gasket body. The laminate layer includes a sealing portion (22a, 52a), having a thickness Da, for sliding on an inner surface (18) of the cylinder in sealing tightness. A liquid receiving portion (22b) has a thickness Db, for contacting the liquid drug in the cylinder. The thickness Da is from 10 microns to 40 microns. The thickness Db is from 20 microns to 50 microns. A ratio R1 of the thickness Db to the thickness Da is from 1.25 to 2.00.
