PURPOSE: To read a picture by a picture quality which resembles an original picture, by detecting the density of a ground of a form before reading the picture image, executing this detection at a position which is as near as possible to said picture image, and reading said picture image by a gradation characteristic being suitable for the detected ground density.

CONSTITUTION: A picture to be read (impression shadow) 2 is positioned so that a frame 1a is superposed on a window frame of a positioning frame plate 3, by which density of a ground of a form in positions 7a, 7b which are as near as possible to said picture 2 is detected by a line sensor 6, it is detected as ground density of the form, is A/D-converted, and a digital (gradation) signal showing a density level is transferred to a gradation characteristic correcting memory 11. In said gradation characteristic correcting memory 11, ground density of the form is read as a parameter, and plural gradation informations to the same density level of the picture element are stored. Accordingly, the gradation information corresponding to ground density is outputted in order from said memory 11.