PURPOSE: To improve heat release efficiency and accelerate a printing speed by providing members having high heat resistance, insulation and thermal conductivity which accurately contact the uneven surface of a printer head between a temperature-increasing part and a heat releasing member.

CONSTITUTION: If the tip of a printer head 101 is allowed to contact a thermal transfer film 111 arranged on a platen 112 while the tip is heated, and then energized, a resistance layer heats to perform printing. At that time, the heat generated increases the temperature of the tip of the printer head. a high thermal conductivity and elasticity heat releasing sheet 103 is closely attached between a heat releasing member 104 of high thermal conductivity material then fixed with a tightening screw 107, thus constituting a head unit. Since the elastic heat releasing sheet 103 is crushed while closely sticking to the printer head temperature-increasing part and the heat releasing member 104, the heat generated is conducted efficiently to the heat releasing member 104, preventing a temperature rising in the printer head temperature-increasing part.