A misalignment correction method for forming a plurality of color images on a transfer belt to form a multi-color image and correcting a misalignment of each color using a detection sensor, including forming a patch by superposing a reference pattern as a last color to be superposed on a color pattern to be corrected, preparing a plurality of patches, arranging the plurality of patches on the transfer belt, optically detecting a value of each of the patches with respect to the shift quantity of the respective patches of the continuously formed patch group in the correction pattern, calculating an intersection point of two approximate lines as output obtained on opposite sides of an inflection point of the two lines, and performing misalignment correction based on the intersection point.