1. A misalignment correction pattern formation method of forming a plurality of color images on a transfer belt to form a multi-color image and correcting misalignment of each color using a detection sensor, the method comprising: preparing a reference pattern with a plurality of lines formed by a black color as a reference color at a predetermined pitch between the lines; preparing a color pattern to be corrected with a plurality of lines formed by a color toner at an equal pitch to the pitch in the reference pattern; forming a pattern as a patch by superposing the reference pattern as a last color to be superposed on the color pattern; preparing a plurality of patches each in which a position of the lines in the color pattern with respect to the lines in the reference pattern is shifted by an optional quantity in a pitch direction of the lines; arranging the plurality of patches on the transfer belt along a movement direction thereof; selecting either one of a patch in which the color pattern to be corrected is completely superposed by the reference pattern and a patch in which the color pattern to be corrected is completely displaced from the reference pattern, the selected patch being set as a reference patch; and forming a continuously formed patch group including the reference patch and the patches as a misalignment correction pattern.