PURPOSE: To extend service life of a recording head by lessening stored-heat at the recording head and raising a recording quality upto higher level by judging heating conditions at the before-last and last times for each heat generating dot, and determining the time length of heating at this time based on the results of the above judgements.

CONSTITUTION: Generation of heat of each heat generating dot from 2aW2g is respectively controlled by each heat generating condition at the before-last and last times. For example, when to record a character A, for each heat generating dot, if any generation of heat at each pitched position did not exist neither at the before-last nor last time, the length of heating time is 0.5ms, if generation of heat at each pitched position at the before-last and last times existed for the former but did not exist for the latter, it is 0.4ms, and if existed at the last time also, it is 0.3ms. Thus, the length of heating time is shorten when to be redriven after 2 pitches for each dot, thereby the stored-heat at a recording head 1 is lower and a constant recording density can be obtained.