In an image reading apparatus, it is judged whether an original sheet is a first sheet type, whose sheet length is longer than or equal to a first conveyance distance and shorter than a second conveyance distance, and a second sheet type, whose sheet length is longer than or equal to the second conveyance path, the first conveyance distance being a distance between a first conveyance roller and a second conveyance roller, the second conveyance distance being a distance between a supply roller and the second conveyance roller. At least one of a leading-edge arriving timing; a trailing-edge arriving timing; and a sub-scanning magnification is set dependently on the judged result. An image is read from the original sheet by using an image reading unit and a conveyance unit based on the set at least one of the leading-edge arriving timing; trailing-edge arriving timing; and sub-scanning magnification.