PURPOSE: To enhance printing quality in a line feed part indispensable to the printing of graphics or animation, by printing the boundary part of the printing of the n-th line and the printing of the (n+1)-th line so that three colors shift stepwise and performing printing so that the reduced part of the printing of the n-th line overlaps with the printing of the (n+1)-th line.

CONSTITUTION: Printing data 29W31 are subjected to lap-printing at the n-th line so as to stepwise shift by one dot and each color of the (n+1)-th line is stepwise shifted from each color of the n-th line so that both colors overlap with each other in an conjugated manner and printing is performed so that the same colors of both lines are overlapped with each other. Yellow Y-data 29, magenta M-data 30 and cyan C-data 31 overlap with each other by one dot in a Y-overlap part 32, an M-overlap part 33 and a C-overlap part 34. For example, in the case of a printer wherein a printing head is constituted of 24 elements of a 1/180 inch pitch and the min. line feed quantity is a 1/120 inch pitch, data is formed so that two higher rank dots of Y-data 35, one higher rank dot and one lower rank dot of M-data 36 and two lower rank dots of C-data respectively become non-printing to perform line feed printing at a 14/120 inch pitch to make it possible to perform printing so that the data of the same color become the overlapped state of one dot and are shifted to a position separate from the other color.