A printer comprising a carriage making reciprocating movement and a printing head mounted thereon, the movement of the carriage comprising an outward section from a home position to the other position, a homeward section from the other position to the home position, and two reverse sections to change the direction of the movement, a printing being made on a printing paper by defining the outward and homeward sections as a printing area, in which, when printing includes a mark printing to print a mark on an edge of the printing paper, the mark printing is carried out by using one of the reverse sections.