Provided is a book cover core body and a kit, which are used for manufacturing a book cover member which allows the original book to be finished easily, accurately, and neatly when an individual prepares an original book according to his taste without having to use an auxiliary tool such as a ruler and a stabbing. In the book cover core body used for manufacturing the book cover member and the kit including the same, at least a front cover core and a back cover core are glued at a predetermined interval (L) to a reverse side of a book cover print sheet with a book cover pattern, a title or the like drawn thereon, the book cover member being equipped with a front cover part, a spine part, and a back cover part, and the book cover core body including the front cover core, the back cover core, and a holding part having the same width as the above-mentioned interval (L), in which the front cover core and the back cover core are held integrally through an intermediation of the holding part, and in which, after the front cover core and the back cover core have been glued to the reverse side of the book cover print sheet, the holding part is separable from the front cover core and the back cover core.