In order to prepare rare earth oxide containing glasses that have high melting temperature, a CO2 laser was employed. This method was shown to be easier than the process of using an electric furnace which is normally used in preparing glass at a high temperature. Glass forming regions of SiO2-Ln2Oy and 0.4CaO · 0.6SiO2-Ln2Oy system (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu ) were investigated and the thermal stability of obtained glasses were evaluated by crystallization peak temperature measured by differential thermal analysis. The glass forming regions of SiO2-Ln2Oy systems were narrower than that of 0.4CaO · 0.6SiO2-Ln2Oy systems. The SiO2-Tb2O3.5 system showed the widest glass forming region while the SiO2-CeO2 system showed the narrowest among SiO2-Ln2Oy systems.