A method of raising the printing speed of an image printing device when time-division drive is performed, utilizes time-division drive using four times divisions. Image data is read out of the editing buffer of a RAM in regular order, in the form of a staircase, four dots at a time, and the image data is rearranged in the form of a staircase of eight dots in a print buffer within the same RAM. This makes it possible to transmit data from the RAM to a printhead one byte at a time in an efficient manner.