A scanner includes a feeding unit, a transport unit provided downstream of the feeding unit, and a first reading unit provided downstream of the transport unit, a second reading unit provided to face the first reading unit across the transport path and configured to be displaceable in a direction of advancing and retreating with respect to the first reading unit, a second medium detection portion as detection means for detecting a specific portion provided in the sheet holder for specifying front and back sides of the sheet holder in which the booklet is sandwiched, and a control unit that determines whether or not a reading surface of the sheet holder faces the first reading unit based on the detection information of the second medium detection portion and executes a front/back side determination processing mode for performing processing based on the determination.