The laser-interferometric method for measuring concentration profiles in compartments of electrodialyzers with a small intermembrane distance is developed using an optical cell with a moveable membrane. The method of laser interferometry is used for determining of the limiting diffusion current density by the minimal interface concentration of the solution. The method of a local distributive analysis of diffusion boundary layers of two-component solutions by two-frequency laser interferometry is proposed and the distribution of concentrations in the sodium chloride-calcium chloride system is investigated.