1. An image inspection apparatus comprising: a first-image obtaining unit configured to obtain a first image generated by scanning a sheet on which a predetermined image has been printed in advance; a scanned-image obtaining unit configured to obtain a scanned image generated by scanning a printed matter produced by printing a second image additionally on the sheet; a second-image obtaining unit configured to obtain the second image; a first registration unit configured to perform registration between the first image and the scanned image; a second registration unit configured to perform registration between the second image and the scanned image; a combining unit configured to generate a master image by combining the first image and the second image based on a result of the registration performed by the first registration unit and a result of the registration performed by the second registration unit; and an inspection unit configured to inspect the printed matter by comparing the scanned image against the master image.