Provided is a tape measure having a length marking function, in which a guide having a slide groove formed at a predetermined distance from a bottom vertically extending from a first side of the casing and an insertion gap spaced from the first side is integrally formed; a threaded hole is formed through a bottom of the guide; a locking ball partially protruding inside the guide, a compression spring elastically supporting the locking ball, and a wrench bolt preventing separation of the locking ball and the compression spring are disposed in the threaded hole; a marker is provided to mark a length of an object pointed by a scale on the metal tape drawn out from the casing.
