A printing mechanism has: a head mechanism including a printing head configured to print on a recording paper; a platen mechanism including a platen roller configured to nip the recording paper with the printing head to feed the recording paper; a fixed blade arranged in one mechanism of the head mechanism and the platen mechanism; and a movable blade arranged in another mechanism of the head mechanism and the platen mechanism in a slidable manner and configured to cut the recording paper with the fixed blade, the another mechanism comprising: a movable blade guide wall arranged upstream of the movable blade in a paper path direction of the recording paper; a first rib protruding from the movable blade guide wall to downstream of the paper path direction; and a second rib formed at a position on the movable blade guide wall, which is separated from the fixed blade with respect to the first rib in a movement direction of the movable blade.