To perform printing on printing paper to its end portion, without depositing an ink droplet on a platen.

Each of recording areas R of image data is determined depending on a kind of each of printing paper sheets P. Each recording area R is set beyond the ends of four sides of each printing paper sheet P. As the printing paper sheet P4 in Fig.1(d) is larger than the printing paper P1 in Fig.1(a), the recording area R4 is set to be larger than the recording area R1. The sliding properties in a sub-scanning direction of the printing paper sheets P1. P2 and P3 are set to be greater in the order of P1, P2 and P3. The lengths of the recording areas R of images in the sub-scanning direction to the respective printing paper sheets are greater in the order of R1, R2 and R3. When the recording areas are determined as in the above, a blank portion is hardly produced at the end of the printing paper sheet. A waste time for printing due to the recording of an image on the unnecessarily large recording area for image data, is also eliminated.