An image reading apparatus of the invention includes an auto document feeder to automatically feed an original document along a conveyance path, a first sensor that is provided on the conveyance path and detects a first passage time of the original document, a second sensor that is provided at a position different from a position of the first sensor in a conveyance direction of the original document and also different therefrom in a direction perpendicular to the conveyance direction and detects a second passage time of the original document, and a skew determination section that obtains a skew amount of the original document from a difference between the first passage time detected by the first sensor and the second passage time detected by the second sensor and determines occurrence of a skew of the original document based on the skew amount.