To provide a correction method of a CCD output, capable of securing the stable CCD output by each read original at all times, without the need for revision, such as redesign of an original read optical system.

In the original reader provided with a light source; a CCD element; a reference white board for shading correction; and an automatic document carrying means for carrying originals one by one each up to the read position on contact glass, and for reading information of the image of the original, by receiving a reflected light in the original on the contact glass from the light source at the read position by means of the CCD element, a luminous quantity detection means is provided at a position in an upper face of which light from the light source is emitted and at the outside of a region of a maximum original width, data for shading correction are corrected on the basis of the output from the luminous quantity detection means so as to ensure a fixed CCD output.