PURPOSE: To make the peripheral member lightweight and also to enhance printing quality by preventing the vicinity of the central spelling part of a booklet from being projected from the printing surface and preventing affecting the peripheral member in a time for printing.

CONSTITUTION: A printer for a booklet is equipped with a printing head 1 for performing printing for the opened and conveyed booklet S and a platen 6 supporting the booklet S oppositely to the printing head 1. The front-position conveyance roller part 2 and the rear-position conveyance roller part 3 consisting of a set of a couple of rollers which hold the booklet S between the rollers and convey the same are equipped in the front position and the rear position for conveying the printing head 1. The roller parts 2, 3 are turned nearly around the printing position of the printing head 1 in the opening/closing direction of the booklet S. A turning command matched with thickness detected by a thickness detection part 13 is sent from a controlling part 20. Either of the roller parts 2, 3 is turned and positioned by a turning positioning part 11 in accordance with the turning command. The projection part T in the vicinity of the central spelling part of the booklet S is withdrawn from the printing surface.