An image reading apparatus which approximates the MTF characteristics on the front and back surfaces of the original to each other, in reading a double-sided original, to thereby prevent a density difference and a color difference from being caused between the front and back surfaces of the original. A CCD line sensor and a CIS read front and back surfaces of the double-sided original to output image data. The filter coefficients of first and second MTF correction filters are set for use in a plurality of areas arranged by dividing respective reading ranges of the CCD line sensor and the CIS. The first and second MTF correction filters correct the MTF characteristics of the image data output from the CCD line sensor and the CIS, using the set filter coefficients for associated areas.