It is known that even mixing only a small amount of Na has effect on electrical and structural property of the CIGS absorber layer and, as a result, device efficiency is improved. In this study, unlike the conventional method where Na diffuses from SLG while CIGS absorber is growing, a new method was applied. In the new method, Na precursor is deposited on the CIGS absorber layer grown on Al2O3/SLG to incorporate Na. The effect of Na on the absorber layer was observed using secondary ion meass spectroscopy, Hall measurement system, scanning electron microscopy, and x-ray diffraction. As a result, it was found that, in the post deposition treated CIGS absorber layer, Na has effect mostly on the electrical property of CIGS without significant change of the microstructure.