In order to extend the potential application of the staining, which has been used only for coloring glasses, we have investigated the Cs-staining as a new staining technique other than Ag and Cu-staining. At first, we prepared new Cs-stains consisting of Cs2SO4-Na2SO4, Cs2SO4-CsCl mixed salts, or CsNO3. The Cs-staining was carried out at 500∼600°Cfor 12∼96 hours using commercially available borosilicate (BK7®) and soda-lime silicate (B270®) glasses as substrates. Elemental analyses and X-ray microanalyses showed that Cs+ ions were incorporated into the surface area of the glass substrates. The refractive indices measured by a prism coupling method at 633nm increased by 0.01 to 0.02. The measurements also indicated that the light was propagated in the stained area showing that the waveguides were successfully formed.