A wide-format printing apparatus can suppress a posture variation of a carriage to improve landing accuracy of ink, and can reduce an HP (head to platen) distance to the minimum gap, thus achieving higher image quality and mass-production performance. The HP distance, the main rail and the sub rail are adjustable, and the curve amount of both rails is made to be in agreement with the curve amount of the platen. After that, the adjustment for minimizing the local deformation of both rails is performed.