A control section of a reading device performs skew judgment based on an image of a preceding document scanned by the reading section to determine whether the side edge portion of the preceding document is displaced into a nip region sandwiched between a feed roller and a separation section. When it is determined that the side edge portion of the preceding document is displaced into the nip region and also the detection section, which detects a document placed on the placement section, detects a subsequent document, the control section determines a transport error.