The invention produces a document-image reading device that can analyze a speed fluctuation state of a scanner when scanning an image in the feed direction by separately extracting speed fluctuation components by determining a change in density of references scale lines; and, on the basis of the analysis result, prevents the occurrence of an image blur that can result from unstable factors of a driving mechanism of the device. The document-image reading device, which reads document image data at a specified time interval given by a reference clock signal, comprises an image sensor that can read a document image while the document-image reading device or the document moves in the feed direction. Additionally, the document-image reading device includes a chart reader for reading a reference chart portion having alternations of high-density and low-density divisions that are arranged one after another at a distance interval equal to the least pitch readable by the document-image reading device. A processor processes image data read from the reference chart portion by using a comb-type filter and by integration.