A gasket (13) for use in a medical syringe is provided, which includes a main body (14) made of an elastic material, and a lamination film (15) provided on a surface of the main body (14). The gasket (13) has a circumferential surface portion (17) to be kept in contact with an inner peripheral surface of a syringe barrel (11) of the syringe. The gasket (13) has a groove (22) provided in the circumferential surface portion (17) thereof as extending circumferentially thereof. The groove (22) has a depth of not less than 0.8D (μm), preferably not less than D (μm), wherein D (μm) is the thickness of a portion of the lamination film (15) present in the circumferential surface portion (17) of the gasket (13).
