A recording head having a plurality of ink discharge element lines arranged thereon is moved in a direction different from the direction of arrangement of the ink discharge elements to conduct a main scan, and at the end of the main scan, a recording medium is moved by a predetermined width in a direction different from the main scan direction to record an image. A record area of the recording head is divided into a plurality (n) of areas and each unit image area on the recording medium is main scanned n times by using the n divided areas of the recording head and thinned images with a print factor of 1/n are sequentially recorded to complete the record of the unit image area. The print factor for the pixels in the boundary area of adjacent unit image areas is lower than the print factor to the entire unit image area in at least one of the n main scans. Thus, the number of pixels recorded by the same main scan in the boundary area is increased. A high quality image without a joint stripe is attained even for a recording medium having a relatively high ink absorption speed.