We present a novel way to fabricate electronic devices from a molecular charge transfer salt Ag(DM)2 by simple illumination, which realizes a junction-structure in the single molecular crystal. The electrical conductivity of the selected parts of samples can be controlled by illimination time and power. The electrical behavior gradually turned semiconducting from metallic one by illumination. X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray absorption fine structure indicated that illumination should transfer some electrons from the conducting DM columns to the Ag ions. The X-ray powder diffraction pattern indicated that original crystal lattice was maintained after the illumination. These observations imply that the illumination practically effected doping (or rather dedoping) on the material.