To read an original in the case of leaving-behind in which a paper jam does not occur so as to easily use an automatic document feeding device and to improve accuracy of flotation detection.

The automatic document feeding device includes: an original guide member 20 which is arranged in a position corresponding to an original reading face 2b, which is a lower face of an automatic document feeding device body 11, so as to be movable in a direction to face and to be separated from the original reading face 2b when the automatic original feeding device body 11 is in a reading posture with a closing operation and which can abut on the original reading face 2b when the automatic original feeding device body 11 is in the reading posture; and detecting means 27 for detecting the flotation of the automatic original feeding device body 11 to the original reading face 2b based on a relative position in a direction where the original guide member 20 is separated from the automatic original feeding device body 11.