PURPOSE: To enable reduction in printing sounds with a higher printing quality by providing an auxiliary guide plate for pressing a medium lightly on a guide plate provided at the tip of the print head in a dot impact type printer for pass books.

CONSTITUTION: As a printing medium 11 starts to be inserted, with the rotation of a step-motor 5, the platen 3 lowers through a gear 4, a shaft 6 and retraction levers 7a and 7b. As the printing medium 11 stops at the printing position, the platen 3 rises with the inversion of the motor 5, hitting a guide plate 13 pinching the printing medium 11 and then, lowers by a given value making it ready for printing. At this point, a fixed space is kept between the printing medium 11 and the printing head 12 and an auxiliary guide plate 14 provided on the guide plate 13 presses the printing medium 11 lightly with a spring 17. This can prevent blurring of printing and lifting of the medium regardless of changes in the thickness of pass books or the like thereby ensuring a high quality printing along with a lessened generation of noises.