PURPOSE: To enable highly precise gradation printing or the like to be performed at high speed by a method wherein electrifying time of each heating element is controlled according to a data value stored in a memory having a plurality of bits storing an input data for each one piece of each heating element.

CONSTITUTION: Every time a clock pulse is inputted, gradation data of each dot cell composed of PIN1-PIN5 are in parallel inputted. Therefore, when 640 of clock pulses CLK are inputted, corresponding gradation data PIN1-PIN5 are stored in each bit cell of shift registers 21-25. After inputting the clock pulse CLK, a printing start command STB signal is inputted, an electrification time control part 30 takes into each bit cell output of the shift register 21. In the case of data to be printed, each printing on signal is outputted every time one electrification pulse signal PLS is inputted in response to said data. A driver corresponding to driver 4-1-4-640 is turned on, and a heating element in said electrification time is electrified.