An image reading apparatus includes a reading unit configured to read an image of a document and generate image data, a filtering unit configured to perform filtering processing on the image data generated by the reading unit and generate image data, a binarization unit configured to perform binarization processing based on the image data generated by the filtering unit using a first threshold value to generate first binary image data, and perform binarization processing based on the image data generated by the filtering unit using a second threshold value to generate second binary image data, and a detection unit configured to detect an edge in the image data generated by the reading unit based on the first binary image data and the second binary image data generated by the binarization unit.