A thermal printer includes an inked ribbon (21), an inked ribbon take-up mechanism, a print head (14) with two arrays (26, 27) of thermal resistance elements (R 11 -R 1n , R 2 ,-R 2n ), a carriage (8) mounting the print head, and a controller (1) for controlling the print operation. The printer is provided with print mode switching circuit which selects low-speed print mode in which one array of thermal resistance elements is activated for each dot pitch for printing, or high-speed print mode in which the two arrays of thermal resistance elements are activated alternately for every dot pitch for printing. The printer having the print head with two thermal resistance elements is capable of high-speed printing and also high quality printing at a low print speed.