Laser-beam scanning – laser-induced breakdown plasma optical emission spectrometry was applied to obtain the elemental distribution in three-dimensional direction for different surface states corresponding to chemically-pretreatments of an Al-alloy sample. The distribution of magnesium oxide inclusion particles could be estimated from the intensity ratio of Mg/Al each for the irradiation points, indicating that chemical-etching and desmutting treatments made the magnesia particles to be reduced both in the lateral and in-depth directions. The resolution of our measurement was within 200 μm in the lateral position and ca. 15 μm in the depth direction, which were mainly determined by the crater size of the laser shot. The objective of this paper is to suggest an analytical technique suitable for evaluating the spatial distribution of inclusion or contaminant particles on the surface rapidly during the chemical surface pretreatment of Al-alloy materials.