1. An image data adjusting device for adjusting the number of pixels of input image data to obtain output image data, said device comprising: a data adjusting table representing magnifications for all the pixels of said input image data per direction in which the number of the pixels of the input image data is adjusted; and a data adjusting section which refers to said data adjusting table to copy each of said pixels serially inputted in a scan direction as many times as represented by the corresponding magnification of said data adjusting table, thereby to obtain said output image data.