To provide a document reader which can correct color stripes, even during a full-color read by a sheet-through system, without having to add additional mechanism to a document feeder.

The document reader, which reads a document by using a sheet- through type document feeder and converts the read color image information into a digitized image signal, is equipped with a color stripe detection part 10331, a color stripe correction part 10332, and a memory 303; and the color stripe detection part 10331 turns on an exposure lamp 28, while at the stage where the document to be read is not inserted to a readout position for reading in the image information by the colors R, G, and B, binarizes only the luminance data of R by a binarization part 10331b, and writes a dust on/off flag to the memory 330; and when the document is read, the image data stored in the memory 303 are read out, the color stripe correction part 10332 corrects the binarized R data by using an interpolation processing part 10332a, and a luminance/color difference reverse conversion part 10332b puts the data back into RGB data and outputs them.