To provide a thermal printer which can perform printing well even under a low temperature environment by thermally insulating a thermal head 15 or a print medium, e.g. a print sheet 2 or a thermal transfer ink ribbon 7, being transported by a platen roller 16 and feeding the print medium under preheated state to a print section 6 of the thermal head 15 and the platen roller 16.

In the transporting passage 4 to the thermal head 15 and the platen roller 16, the print media 2 and 7 are insulated thermally over a specified area. The print media 2 and 7 are transported while being held between the thermal head 15 and the platen roller 16 and printed by means of the thermal printer 1 wherein a section 5 for thermally insulating the print media 2 and 7 is provided along the transporting passage 4 of the print media 2 and 7.