A method of thermally printing a multicolor image on a print paper is disclosed. With this method, a lengthy multicolor image can be printed on a paper over a plurality of pages of a length determined by a length of each ink zone of an ink ribbon. First, the ink ribbon is set over a platen roller with the paper being interposed therebetween, the ink ribbon having plural groups of ink zones, the ink zones of each group carrying a plurality of heat-dissolving inks of different colors, respectively. One of the ink zones is positioned at a printing position where a thermal head contacts with the platen roller through the ink ribbon and paper. The thermal head is then activated in accordance with image data stored in a memory, and the ink ribbon and paper are advanced to effect transfer of ink so that one of color component images of the image is printed on the paper. The ink ribbon and paper are then advanced by a predetermined distance to separate the paper from the ink ribbon. The paper is then backwardly moved by a distance equal in length to the total advance of the paper effected in the transferring of ink and the separation of paper. The above operation is cyclicly carried out with respect to the other ink zones to form the multicolor image on the paper without effecting the backward movement in the final cycle. If image data is still present in the memory or if a command for causing the print operation of the image to continue is received, the paper is backwardly moved by a distance substantially equal in length to the advance of paper in the final separation of the paper.