A non-intrusive technique for ion concentration measurements was realized using coherent anti-Stokes Raman scattering (CARS) microscopy in two different solutions. CARS exhibits high sensitivity, non-intrusiveness and chemically-specific measurement capability. Na2SO4 and NH2Cl solutions, which have characteristic Raman-peak at different wavenumbers, were used for the measurements. CARS arising from the solution measured on two microscopes simultaneously to measure the reference value and CARS intensity ratio was calculated. The calibration curve showing the relationship between the CARS intensity ratio and solution concentration was obtained. Further investigations of mixed solution including Na 2SO4 and NH4Cl will be carried out to validate the present technique.