1. A method, executed by an image reading apparatus, of detecting a floating amount of an original from an original table, the image reading apparatus including the original table on which the original is placed, a line sensor, and a lens array configured to guide light from the original to the line sensor, the method comprising: obtaining, executed by the image reading apparatus, of image information of the original at least via the line sensor and the lens array; extracting, executed by the image reading apparatus, of a characteristic frequency by frequency analysis of the image information; and detecting, executed by the image reading apparatus, of the floating amount based upon the characteristic frequency.