A scanner connected to an external device through a network is provided. The scanner includes, a reading section that reads an image recorded on a sheet so as to generate image data, an image data group supply section that, in a case where a plurality of images recorded on a plurality of sheets are read by the reading section, sequentially generates an image data group every time a part of the plurality of sheets is read by the reading section, and sequentially supplies the generated image data group to the external device, a joint information generation section that generates joint information used to join two or more of the image data groups, the two or more of the image data groups representing the plurality of images; and a joint information supply section that supplies the joint information to the external device.