A composite container lid includes an inner plug 1 with a flow-out port and an upper lid 3 detachably attached to a container mouth portion 80, wherein: the inner plug 1 includes an upper lid engaging cylinder 5, a container mouth portion-securing member 7 having a circumferential wall 9 that surrounds the upper lid engaging cylinder 5, and linking pieces 11 that link the inner surface of the circumferential wall 9 to the upper lid engaging cylinder 5 so as to form a flow-out port 13; the upper lid engaging cylinder 5 is provided, on the upper end portion of the outer surface thereof, with a circumferential protuberance 5a for temporary engagement; engaging pieces 37 are formed on the inner surface of a top plate 31 of the upper lid 3, the engaging pieces 37 having an undercut 37a for temporarily engaging with the circumferential protuberance 5a that temporary engages with the upper lid engaging cylinder; and a sound-suppressing protrusion 50 is provided in a region surrounded by the engaging pieces 37.