An image reading apparatus is disclosed. The image reading apparatus includes an automatic document feeding unit that transports a document in a predetermined direction while the document floats above a platen glass member and a light source disposed below the platen glass member that irradiates a portion on the document at a predetermined reading location such that reflected light from the portion on the document is converted into image data and a floating distance between the document and the platen glass member is detected to set a value of an image parameter for correcting the image data for the document, based on the detected floating distance between the document and the platen glass member.