A printing method comprising supplying print data composed of a multiplicity of dot information to a printing head wherein the printing head has a plurality of dot forming elements arrayed along a sub-scanning direction, the method comprising the following steps: moving the printing head in a main scanning direction with respect to a printing medium and printing an image on the surface of the printing medium, thereafter moving the printing medium in a sub-scanning direction by a specific transportation quantity with respect to the printing head, wherein, seen in the sub-scanning direction, in the end portions of the print data supplied in every main scanning operation of the printing head, a deformed data portion is formed that has a 100% print rate region, an intermediate print rate region, and a 0% print rate region, wherein the deformed data portion is formed so that a boundary line between the intermediate print rate region and the 0% print rate region and a boundary line between the intermediate print rate region and the 100% print rate region have an undulating waveform, wherein a print on each region corresponding to a transportation width of the printing medium of one time in the sub-scanning direction is completed by moving the printing head with respect to the printing medium in the main scanning direction a plurality of times, - wherein, in the first time of moving the printing head with respect to the printing medium in the main scanning direction, first print data are printed where the deformed data portion is formed in the printing medium, - wherein, in subsequent times of moving the printing head with respect to the printing medium in the main scanning direction, print data which extend across a previous region already printed and a next region are sequentially printed in the previous region already printed, and - wherein, in the last time of moving the printing head with respect to the printing medium in the main scanning direction, print of a remaining portion of the deformed data portion of the region, where the first print data were printed, is completed. moving the printing head in a main scanning direction with respect to a printing medium and printing an image on the surface of the printing medium, thereafter moving the printing medium in a sub-scanning direction by a specific transportation quantity with respect to the printing head, wherein, seen in the sub-scanning direction, in the end portions of the print data supplied in every main scanning operation of the printing head, a deformed data portion is formed that has a 100% print rate region, an intermediate print rate region, and a 0% print rate region, wherein the deformed data portion is formed so that a boundary line between the intermediate print rate region and the 0% print rate region and a boundary line between the intermediate print rate region and the 100% print rate region have an undulating waveform, wherein a print on each region corresponding to a transportation width of the printing medium of one time in the sub-scanning direction is completed by moving the printing head with respect to the printing medium in the main scanning direction a plurality of times, - wherein, in the first time of moving the printing head with respect to the printing medium in the main scanning direction, first print data are printed where the deformed data portion is formed in the printing medium, - wherein, in subsequent times of moving the printing head with respect to the printing medium in the main scanning direction, print data which extend across a previous region already printed and a next region are sequentially printed in the previous region already printed, and - wherein, in the last time of moving the printing head with respect to the printing medium in the main scanning direction, print of a remaining portion of the deformed data portion of the region, where the first print data were printed, is completed. - wherein, in the first time of moving the printing head with respect to the printing medium in the main scanning direction, first print data are printed where the deformed data portion is formed in the printing medium, - wherein, in subsequent times of moving the printing head with respect to the printing medium in the main scanning direction, print data which extend across a previous region already printed and a next region are sequentially printed in the previous region already printed, and - wherein, in the last time of moving the printing head with respect to the printing medium in the main scanning direction, print of a remaining portion of the deformed data portion of the region, where the first print data were printed, is completed.