A document feeder includes: a document detecting device arranged on the top of the copier body, for detecting a document inserted from the outside; a feed roller arranged adjacent to the document detecting device, on the top of the copier body, for feeding an inserted document into a space between the original table and the original cover, in response to the detection of a document by the document detecting device; and an original cover lifting device arranged on the top of the copier body, for lifting the original cover to create a gap between the original table and the original cover, in response to the detection of a document by the document detecting device. Alternatively, the feed roller further has a rotary cam on its shaft, so that the cam rotates to lift the original cover up as the feed roller rotates in the document feeding direction. Then, after the document is fed in place, the feed roller is reversely rotated in a constant time, whereby the document cover is sunk to press the document onto the original table.