PURPOSE: To shorten a printing time by dividing image data to process the same in a thermal sublimation type printer.

CONSTITUTION: The upper and lower bits of image data are respectively stored in an upper buffer 101 and a lower buffer 102 and pulse rows are formed at every upper and lower buffers to reduce the number of times of serial transmission. Strobe signals different in width with respect to the upper and lower buffers are formed on the basis of the control of a controller 106 by a strobe signal generator 107 and the pulse rows of the strobe signals are arranged so that upper and lower pulses continue to realize a printer shortened in printing time and reduced in density irregularity.