The thermal transfer printer of the present invention prevents slackening of recording paper by exerting a braking force upon a recording paper roll to give a back tension to the recording paper when one of the colors of an ink sheet coated with inks of a plurality of colors is thermal-transfer-printed. The recording paper is unwound from the roll thereof in the forward direction and by rotating the recording paper roll in the backward direction the recording paper is rewound. A roller for carrying the recording paper is stopped or braked at the downstream side of the platen when the recording paper is carried in the backward direction for the thermal transfer printing by the next color.