PURPOSE: To enable to control recorded density in accordance with gradation characteristics, by a method wherein time data A for impressed pulses read from a one-line memory and time data B for impressed pulses fed from a counter are compared with each other, and passage of electric currents to heating element dots is stopped when A≤B.

CONSTITUTION: An input signal (a) is converted into gradation data by an AD converter 1, and by the gradation data and heating element dot position data fed from a divide-by-1728 counter 11, predetermined impressing time data A are read from a ROM10 for controlling gradation, and are stored into the one-line memory 2. the data A are read from the memory 2 in accordance with outputs from divide-by-64 and divide-by-27 counters 3, 4 for counting clock pulses. Impressed pulse time data B are outputted from a timer counter 13, and are compared with the data A by one-dot amount at a time by a digital comparator 16. Only when A>B, a high-level signal is fed to a 64-bit shift register 14, and when all the data are supplied, they are latched by a 64-bit latch 15, and a recording action is performed one time. Accordingly, the recorded density can be finely controlled in accordance with resistance characteristics of the heating element dots and the gradation characteristics of a recording material.