Long lasting phosphorescence has been observed in CaO-Al₂O₃-SiO₂ glasses doped with Eu²⁺ and Nd³⁺ after irradiation with an Hg lamp. The emission is due to the 4f-5d transition of Eu²⁺. The phosphorescence wavelength varies from 500 to 600nm, depending on the glass composition. The variation of phosphorescence wavelength is caused by the change of environment around Eu²⁺ ions with glass composition. Analyses of thermoluminescence glow curves reveal that the depth of electron or hole trap level which contributes to the phosphorescence process ranges from 0.50 to 0.81eV. It is thought that these are suitable values for the occurrence of thermoluminescence at around room temperature which results in the long lasting phosphorescence.