PURPOSE: To develop paint function without being effected by the capacity of a buffer register by a method wherein the start point of the next color printing is stored in a system part and subsequently outputted to a printer main body to perform the color printing of a closed region at every unit divided coloring region.

CONSTITUTION: When color printing is started, the data of a divided printing region 3A is supplied to the buffer register of the PRT part 5 from a system part 6 to be stored therein. Since the region 3A is in an initial state, the data of the next divided printing region 3B is supplied to said buffer register to be stored therein. Thereupon, in a step ST6, the searching of the color printing part within the closed region 1 in an one-dot line and the color printing to the detected color printing part are applied from the internal conversion point whose Y- coordinates are uppermost among three internal conversion parts 7A, 7B, 7C. Next, it is judged whether color printing is finished in a line lower by one dot. Then, it is judged whether buffer capacity is finished in the next dot line and, when the buffer capacity is not yet finished (in the case of NO), a dot line to be subjected to color printing is lowered by one line and, thereafter, color printing is again returned to the step ST6.