PURPOSE: To prevent a stepping motor which drives a platen from stepping out by reducing a load on the platen by a method wherein a displacement means which varies the axial relative position of the platen to a thermal head, is provided.

CONSTITUTION: A displacement means 30 which displaces selectively a platen 16 or an abovementioned thermal head 17 relatively along the axial direction of the platen 16 is provided on a base 29 located below the platen 16. The displacement means 30 is composed of a rack 32 fixed to a platen frame 31, and a gear 32 engaged with the rack 32, and a plurality of guide shafts 36 guiding the platen frame 31 freely slidably are disposed in upright. When a range wherein the platen 16 comes in direct contact with the thermal head 17 becomes long, the platen 16 is axially displaced and a lap quantity with respect to the thermal head 17 is lessened according to the width size A of paper 11. The range wherein both come in direct contact with each other without any existence of the paper becomes extremely short. A load which the platen 16 receives from the thermal head is reduced, and a stepping motor 21 is prevented from stepping out.