the width of the overlapping region between the heads 1 13 and 2 16 are calculated from this position relationship to rewrite values stored in the position memory 17 it is to be noted that details of a calculation method will be described later with reference to fig4 when an actual image other than the test pattern is printed binarized image data is input into the input image memory 10 the position information stored in the position memory 17 is read and the input image data is accordingly transferred to the temporary memories 12 15 and printed by the heads 1 13 and 2 16 next fig2 is a diagram showing a constitution of a second embodiment of the present invention as shown in fig2 first binary test pattern image data of a straight line extending in an arrangement direction of nozzles of heads 1 24 and 2 28 is input into an input image memory 20 at this time in a position memory 29 a transfer start position in which the correction of the positional shift between the heads 1 24 and 2 28 is not considered address on the memory indicating the top position of each line during the reading from the input image memory 20 a transfer destination position address on the memory indicating the top position of each line during writing into temporary memories 22 26 and the width of the overlapping region initial value is 0 are stored an image transfer section 21 refers to the position information stored in the position memory 29 and transfers input test.