Abstract: According to an image data correction conversion circuit and a skew quantity correction method respectively according to the present invention, image data for predetermined lines is stored, the quantity of skew of the stored image data is measured, the number of blocks into which the image data is divided is operated based upon the quantity of the skew and a control signal for correcting and converting the image data based upon the operated data is output. A selector acquires image data the quantity of skew of which is corrected by selecting and outputting the stored image data for predetermined lines according to the control signal.