PURPOSE: To provide a passbook processing device capable of always corresponding to a change in the thickness of a passbook.

CONSTITUTION: A medium length judging part 42 judging the length of a passbook in a feed direction, a printing start line confirming part 45 confirming the length from the leading end of the passbook in the feed direction to a printing start line, a stepping motor 34 moving a platen in parallel to the feed direction of the passbook, a platen position memory part 44 storing the position of the platen and a control part 46 selecting the position of the platen from the judged length of the passbook, the length up to the printing start line and the stored position of the platen to move the platen through a moving means are provided.