A thermal printer in which a sheet of recording paper is held by and between a thermal print head includes a plurality of heat generating elements and a platen drum, the amounts of heat of the heat generating elements are selectively changed, and an image is printed onto the recording paper. In the thermal printer, a printing position is set just behind a clamp position at which a clamp clamps the leading end of the recording paper onto the platen drum. Therefore, the image printing can be started immediately after the clamp position passes through the thermal head, with the recording paper being in part wound around the platen drum by the thermal printer. As a result, the time taken from paper feeding to printing starting can be reduced.