An image reading apparatus includes: a document size detector that detects either a length or a width of a fed document before reading, and associates the document with a standard size equal to or approximate thereto; an image reading device that reads a document and surroundings thereof at a reading position; a background color plate to be read as an image of the surroundings; a document area determiner that determines a document area; and a blank page determiner that determines a blank page determination area for determining whether a document is a blank page or not. When either of the detected length or width is equal to or more than a predetermined threshold value, the blank page determiner determines the blank page determination area, based on the associated standard size, and otherwise determines the blank page determination area, based on the document area.