There are provided an ink jet printer capable of printing efficiently by reducing the useless operation dependent on the width of a print image to thereby increase the printing speed and an image printing system incorporating the ink jet printer, as well as printing methods therefor. In one aspect, a print head capable of simultaneously printing M dots at a predetermined nozzle pitch in an X-axis direction is scanned in the X-axis and a Y-axis direction, to print an image on a medium. The print image width in the Y-axis direction is detected. Depending on the width, a head moving pitch in the X-axis direction relative scan is determined. The scanning of the head in the X-axis direction relative to the print medium prints maximum M dot lines along the X-axis juxtaposed in the Y-axis direction. The scanning of the head in the Y-axis direction is effected by moving the head relative to the medium at the head moving pitch, after printing by the scanning of the head in the X-axis direction. In another aspect, odd number-time printing is carried out in a predetermined area such that the head starts from a starting point to an end point along a predetermined path. Even number-time printing is carried out in the predetermined area such that the head starts from the end point to the starting point along the path. After each printing, the medium is fed in the X-axis direction by an amount of the unitary print image.