PURPOSE: To enable opening of pages of both longitudinal and lateral types of booklets by means of the same open-page means, by varying the traveling distance of a turning member for opening the page of a booklet according to the stitching direction of the booklet.

CONSTITUTION: When a page of a longitudinal booklet P is opened, it can be opened through similar operation to that of a lateral booklet except the method of keeping the booklet with a weight. In other word, a turn roller 33 rotates to the left and a push-up plate 41 pushes up a booklet P' thus starting the turning operation. After turning, the turn roller 33 keeps rotation to the left and compares the situation with that in the case of a lateral booklet so as to allow laying-down of the turning page only after the turn roller 33 advances near to the right end. When the booklet P' is carried to the left and held between the rollers 47a, 47'a, the rollers, 48'a, 49'a, 50'a which keep the turned side with weights are retreated then the turn roller 33 is further advanced to the right so as to lay down the turning page completely and contact tightly, thereafter the booklet P is also carried to the left so as to contact more tightly. Since the traveling distance of the turning member is varied according to the stitching direction of booklet, the page can be turned reliably according to the type of booklet.