An image reading apparatus includes a reading unit that reads a document transported in a second scan direction, a detector unit that detect a position of an edge of the document in a first scan direction crossing the second scan direction, a setting unit that sets a search range of the edge of the document in the first scan direction, the search range including the position of the edge detected by the detector unit, and a search unit that, on image data that the reading unit has read from the document, searches for the position of the edge within the search range of the edge set by the setting unit.