To obtain an optimum image, regardless of the change of a usage environment and of an individual difference for every copy machine by executing reading MTF correction by means of MTF correction parameters which are obtained from the calculation result of an MTF correction parameter calculating part.

A read MTF calculating part 22 reads data after shading a read MTF correction calculating chart, calculates the read MTF correction parameters concerning the data, sets the read MTF correction parameters and executes read MTF correction. A reflection light from the chart is photoelectrically converted by a CCD sensor 12, converted into digital image data by an A/D converting part 14 and corrected by shading in a shading correction part 16. Then reading MTF characteristics in main scanning and sub- scanning are calculated. A read MTF correction parameter setting part 24 sets the read MTF correction parameters, reading MTF correction is executed by the parameter and the image is processed in an image processing part 20.