PURPOSE: To provide the method and device for picture processing capable of efficiently and accurately setting the reset threshold value for binarization on the picture data in the case of the failure of the reading of one picture data when the image pickup of an area to be photographed is performed by at least two image pickup means and a detection object is read after binarizing the picture data.

CONSTITUTION: When first picture data is processed by an initial threshold value Fos and second picture data is processed by an initial threshold value Fns, the reset threshold value on the second picture data is set by associated with the initial threshold value Fos in either area of the minimum value areas Ma1 or Ma2 in the case that the reading is succeeded in the first picture data and the reading is failed in the second picture data where two minimum value areas are on a threshold value Ft with the minimum difference between a quasi- detection character number Ni to be assumed as a detection character and a detection character number M.