A thermal printer in which papers in a plurality of different widths are usable is configured of a platen roller unit including a platen roller; a thermal printhead unit including a thermal printhead and an exothermic element array; and a plurality of bias elements arranged on the thermal printhead in a width direction to press the thermal printhead onto the platen roller, in which the number of the bias elements is a value obtained by dividing a maximum width of the different widths by a highest common factor of the different widths; the bias elements are arranged with an equal interval which is the highest common factor of the different widths; and among the bias elements, a bias element arranged outside of the width of a paper in use is configured not to apply a load to the thermal printhead to press the platen roller.