Abstract: A built-in core body (10) for forming a ready-made knot of a necktie, by which a neat knot (4) is easily formed and permanently maintained, comprising an outer shell (11), a presser member (12), and a release member (13). A narrow band (2b) of a tie body (2) is inserted in a channel (17) formed in the interior of the outer shell (11) in a double-folded state and the knot (4) is formed around the core body (10) in a conventional manner. The upward movement of the narrow band (2b) through the core body (10) is inhibited by the action of the presser member (12) while the downward movement thereof is free. Upward movement of the narrow band (2b) is allowed when the release member (13) is operated to release the presser member (12) from engagement with the narrow band (2b).