Image reading apparatus

An image reading apparatus configured to read an image of a document by causing a scanning drive unit to perform scanning drive of a reading unit, the image reading apparatus comprising:

• a first drive source;
• a second drive source;
• a transmission unit that transmits a driving force from the first drive source to the scanning drive unit, wherein the transmission unit has a first coupling configured to transmit the driving force from the first drive source to the scanning drive unit with a first speed reduction ratio, a second coupling configured to transmit the driving force from the first drive source to the scanning drive unit with a second speed reduction ratio being larger than the first speed reduction ratio, and a selector which is movable, by the second driving source, between a first position at which the selector connects to the first coupling and a second position at which the selector connects to the second coupling;
• a detector configured to detect that the selector connects to the second coupling;
• and
• a controller configured to control driving of the second drive source so as to move the selector from the first position to the second position with the reading unit being stopped at a predetermined position and subsequently cause the first drive source to repeat driving in increments of a predetermined amount until it is detected by the detector that the selector connects to the second coupling.