An image reading apparatus to prevent reading quality from deteriorating when two reading units respectively read a first side and a second side of a document with different capabilities, and a method of controlling the same includes an automatic document feeder to feed a document, a first reading unit to read a first side of the document fed by the automatic document feeder, and a second reading unit to read a second side of the document fed by the automatic document feeder. A control unit to control an operation of the image reading apparatus determines at least one of the first reading unit and the second reading unit as a reference reading unit in a both-side reading mode in which both sides of the document are read and controls a transport speed of the document such that the document is transported at a speed to allow the reference reading unit to read the document.