PURPOSE: To ensure an accurate control of temperature and to obtain a print pattern of a certain level of concentration, by driving a heating resistance element of a heat-sensitive recorder with a constant current, monitoring the voltage drop of the heating resistance element and then cutting off the driving current at a time point when the voltage drop reaches a certain level.

CONSTITUTION: A drive input signal S1 actuates a constant current driving circuit 2 through a gate circuit 1 in the case of a driving input that indicates the recording of a dot pattern provided in accordance with the heating resistance elements Rh1∼Rhn of a heat-sensitive head 3. Then the corresponding elements Rh1∼Rhn are selected and driven by a constant current. Here the temperature change of the heating resistance element is detected from the change of the voltage drop which is caused by the fluctuation of the resistance value. When this voltage change reaches a certain level, the electric conduction is stopped to the elements Rh1∼Rhn. Thus the temperature is controlled at a prescribed level.