1. An image reading device, comprising: an imaging device including a plurality of imaging elements arranged in line; a color measuring unit configured to detect a level of light reflected from an object at a color measurement area to output an electric signal reflecting color of the object; a calibration plate having a surface on which a plurality of color patches is formed; and a processor configured to: cause the color measuring unit to read the plurality of color patches while changing a relative position between the plurality of color patches and the plurality of imaging elements, to output color measurement results of the plurality of color patches; generate a set of reference values for the plurality of color patches based on the color measurement results of the plurality of colors; cause the imaging device to read the plurality of color patches while changing a relative position between the plurality of color patches and the plurality of imaging elements, to output reading results of the plurality of color patches; compare the reading results of the plurality of color patches, with the set of reference values for the plurality of color patches, to generate a comparison result; and generate a set of correction values based on the comparison result, the set of correction values being used for correcting the reading results of the plurality of color patches.