A scanner includes a transport mechanism that continuously transports a plurality of documents, a sensor, a control unit that performs correction of a read image which the sensor reads by using a correction value, a calculation unit that calculates the correction value based on a result from which the sensor reads a reference region between the documents, and a storage unit that sequentially stores the correction value in any of a plurality of storage regions, in which the control unit switches the storage region where the correction value used for the correction is read out to the storage region where the calculated correction value is stored, if storing of the calculated correction value is completed.