A container closure formed from a synthetic resin as a single unit has a circular top panel wall and a cylindrical skirt wall extending downwardly from the peripheral edge of the top panel wall. An outer cylindrical sealing protrusion, an inner cylindrical sealing protrusion, and annular sealing ridge, all having a predetermined shape and a predetermined size, are formed on the inner surface of the top panel wall. In one embodiment, the thickness of the center portion of the top panel wall is reduced to a predetermined range and a plurality of ribs having a predetermined thickness are formed on the inner surface of the center portion of the top panel wall.