CdSe quantum dots (QDs) were precipitated in silicate glasses under various durations and temperatures of heat-treatment. Absorption and photoluminescence (PL) spectra of the QDs showed the quantum confinement effect from CdSe QDs. When the glass was heat-treated for 10 h, estimated average QD sizes increased from 5.2 nm when the glass was heat-treated at 490 °C and to 6.9 nm when it was treated at 500 °C. When the glass was heat-treated at 480 °C, estimated average QD sizes were 4.9 nm after 20 h and 5.3 nm after 30 h. The PL peak position was independent of the excitation wavelengths; this result indicates that the size distribution of CdSe QDs was narrow.