To provide a string bookmark of a book made attachable and detachable.

The surface part 1 of the partial cover 10 of the book with the string bookmark is applied to the spine 12 of the book 11 and a cover 13, and an insertion piece 4 is inserted inside the cover 13 to be mounted on the cover 13. When the book 11 is closed, the partial cover 10 of the book with the string bookmark is fixed to the book 11 by the force for holding the spine 12 of the book 11 and the cover 13 and the book can be used in the same way as the book with the string bookmark. Further, one or several string bookmarks can be attached corresponding to a use purpose and a thick dictionary documents or the like can be efficiently read. In the unnecessary case of the string bookmark, the book is opened and the partial cover 10 of the book with the string bookmark is drawn out upwardly and the string bookmark can be simply detached.