A document table is provided with a first chart portion and a second chart portion. In each of the first chart portion and the second chart portion, a reference chart is formed. The first chart portion is disposed at an upstream chart position, and the second chart portion is disposed at a downstream-side position located away in a sub-scanning direction from the upstream chart position. On the basis of respective chart images of the first chart portion and second chart portion obtained from respective reference charts of the first and second chart portions read by a document reading portion, the image processing portion obtains respective sharpening levels for respective image areas of a document image of a document read by the document reading portion and, based on the respective sharpening levels, processes the document image.