To provide a lid member for use in sealing a container containing liquid therein, which facilitates unsealing at any time even by a person with weak force, and to provide a liquid container using the lid member and a product containing the liquid, using the lid member.

The lid member is for use in sealing a container containing the liquid therein, and formed of: a resin cap base which is screwed and mounted onto an upper opening of the container containing the liquid therein; a disk portion which is arranged and abutted on a lower surface of an upper bottom portion forming an upper surface of the cap base; a closing member which has an annular protrusion protruding downward from the disk portion to be fitted into the upper opening of the container; and a thermoplastic elastomer which is arranged on a peripheral surface of the cap base, filled in a plurality of grooves extending in parallel with an axis of the cap base, and formed in one body with the cap base.