A print data generating device includes: (a) a display; (b) a print-image-region selector for selecting a print image region which is a region of an original-data-based image, such that the selected print image region corresponds to each of desired images; (c) a media size recognizer for recognizing a size of a print medium; (d) a print layout determiner for determining, based on a size of the print image region and the recognized size of the print medium, a print layout of the desired images that are to be printed onto the print medium, such that a number of the desired images printable onto the print medium is maximized in the determined print layout; and (e) a display controller for causing the display to display a print layout preview showing the desired images that are arranged according to the determined print layout. The print data generating device generates a print data which is used for printing, in conformity with the print layout preview, the desired images arranged according to the determined print layout, onto the print medium.