Abstract: A movement unit moves a reading unit in a first direction and a second direction. A control unit controls the movement unit so that the reading unit is positioned in a predetermined region in a case when a transition is made from an operation mode to a non-operation mode and controls the movement unit to cause the reading unit to move from the predetermined region to a position at which a white reference plate can be read in a case when a transition is made from the non-operation mode to the operation mode. The control unit causes movement of the reading unit by the movement unit to stop when a movement amount of the reading unit measured by a measurement unit becomes a movement amount corresponding to a distance from the boundary to a position at which a white reference plate can be read.