An object is to improve image quality in panoramic printing using a thermal printer. The thermal printer includes a seam shape calculator and a controller. The seam shape calculator determines the position and shape of a seam between images on the basis of an index of inconspicuousness to human eyes, in panorama printing where a panoramic image longer than a specified printing size is divided into the images as small as or smaller than the printing size, and is printed multiple times so that the images are joined to each other. The controller controls a printing medium, an ink ribbon, and a thermal head so that the images divided based on the position and shape of the seam are thermally transferred onto respective continuous regions of the printing medium using unit printing regions of the ink ribbon, so as to be joined to each other.