1. An image reading device, comprising:a processor,
wherein the processor executes:
a whole image generator that divides a read area of a document placement table into a plurality of areas, multiple times executes read processing that collectively reads an image of a document in the plurality of areas, and generates a whole image that corresponds to a whole of the plurality of areas in each read processing;
an extractor that extracts an individual image corresponding to the document from the whole image;
an image file generator that generates a plurality of image files in which a plurality of individual images acquired by executing each read processing are collected by the plurality of areas;
a second determiner that determines, based on the plurality of individual images acquired by executing the each read processing and collected by the plurality of areas, whether or not there is an area among the plurality of areas, in which a document characteristic has changed in the each read processing; and
a notifier that notifies a user that there is the area in which the document characteristic has changed in the each read processing if the second determiner determines that there is the area in which the document characteristic has changed in the each read processing.