A reading apparatus includes an image reading unit that reads an image line-by-line and generates an image signal, a signal processing unit that performs signal processing on the image signal, a reference clock generation unit that generates a reference clock signal, and a PLL unit that generates a driving clock signal from the reference clock signal to be supplied to one of the image reading unit, the signal processing unit, and the reference clock generation unit. Skew in the synchronization between the reference clock signal and a driving clock signal is detected, and in the case where skew in the synchronization has been detected during image reading operations performed by the image reading unit, the image reading unit is controlled to read the image having returned to a position that is a predetermined number of lines previous to the current reading position.