To solve the problems when storing the page number for the next reading in interruption of reading by the insertion of a bookmark, a cord, a paper piece or the like or the turning of the angle of the page that the inserted matter is often slipped out to lose the read position in the insertion of the bookmarker, cord or paper piece, and the turning of the angle of the page damages the book itself, and it is serious particularly in the case of a lent book or important book.

The page number in the interruption of reading is stored in an external means not related to the book itself, whereby conventional problems or subjects are solved. Namely, this small-sized device comprises a number reading part, a storage part of the read page number and a display part for the stored page number to store the page number in the interruption of reading. As a concrete example, the small-sized device has a ring-like shape, and it is mounted on the thumb or the like during reading to read and store the page number in the interruption of reading. In the restart of reading, the stored page number is displayed to grasp the page to be restarted.