A thermal printer includes a chassis, a thermal head secured to the chassis and a platen roller which is rotatably supported in the chassis and movable relative to the thermal head. The platen roller is rotated by first platen driving mechanism, while being moved toward and away from the thermal head by second platen driving mechanism. When the platen roller is moved to contact with the thermal head via an ink ribbon intervened therebetween, a data or image is printed on a printing medium fed between the platen roller and the ink ribbon.