We investigated tritium (T) release behavior from silica glass. The specimens were 8 kinds of commercially available silica glass. T was injected by the 6Li (n,α)T reaction of sintered pellets of lithium oxide (Li 2 O) into the silica glass with thermal neutrons in JRR-2 (VT-8) up to 5 × 10 18 neutrons/cm 2 at ambient temperature (about 350 K). After irradiation, the Li 2 O pellets were removed from the silica glass, and T release from the silica glass was measured in a flow of hydrogen (H 2 ) or ammonia (NH 3 ) sweep gas at atmospheric pressure at a constant heating rate of 2 K/min between 675 K and 1375 K with a proportional counter. In the case of H 2 sweep gas, a maximum tritium release rate was observed around 1023 K, while in the case of NH 3 sweep gas, two peaks around 1023 K and around 1123 K or a peak around 1123 K with a shoulder were obserbed. After the experiments of T release, FT-IR spectra showed a decrease of SiOH bands at 3650 cm -1 . On the other hand, no changes in intensities at 2250 cm -1 due to SiH were observed for both samples before and after T release.