Abstract: A serial printer comprises a printing head, a carrier for carrying the printing head, a platen, and a pair of guide members extending in parallel with the platen for supporting the carrier in a movable manner. An openable member is attached openably to the casing of the printer and supporting one of the guide members. Engaging receivers are formed in the carrier for allowing the one guide member to engage therewith and disengage therefrom in a direction substantially perpendicular to the extending direction of the one guide member. Engaging brackets may be mounted on the printing head for coming into and out of engagement with one of the guide members at a right angle with respect to the extending direction of the one guide member. Moving members may be supported movably in the casing of the printer for supporting the one guide member, when moved, to bring the one guide member into and out of an engagement with the engaging brackets.