An image reading apparatus includes: a sheet feeding device; a sheet feeding control section that controls transport of an original document performed by the sheet feeding device; a reading section that reads the original document so as to output image data; a reading control section that allows the reading section to perform the reading by repeatedly outputting a reading signal to the reading section; a buffer that temporarily stores the image data; and a monitoring section that monitors a volume of the image data stored in the buffer. When the monitoring section determines that the volume of the image data is less than a predetermined first threshold value, the sheet feeding control section accelerates the transport of the original document and maintains the transport at a predetermined speed, and the reading control section starts the output of the reading signal when the transport of the original document is started.