An image reading apparatus includes a transfer device for transferring a sheet, and a reading device for reading an image of the sheet at a prescribed read position. A light volume detection device is arranged at a position of one side end in a direction perpendicular to a transfer direction of the sheet to be transferred to detect the light volume according to a deviation amount at a sheet transfer position in a direction perpendicular to the transfer direction of the sheet end. An operation device calculates the deviation amount with respect to a reference position of the sheet transfer position from a difference between the light volume detected by the light volume detection device when the sheet is not present at the sheet transfer position and the light volume detected by the light volume detection device when the sheet is transferred to the sheet transfer position.