A document scanning device, configured to sequentially eject and insert sheets under a stack of already-ejected sheets, includes a feed tray, a document table, a catch tray, a feeder feeding sheets from the feed tray to the catch tray, a scanner performing scanning in one of a first mode to scan the sheets fed by the feeder and a second mode to scan a sheet placed on the document table, an ejection detector detecting a sheet on the catch tray, and a controller. In response to an instruction to start the scanning, the controller forbids the scanner to start the scanning when determining with the ejection detector that a sheet is on the catch tray, and allows the scanner to start the scanning in a selected one of the first mode and the second mode when determining with the ejection detector that no sheet is on the catch tray.