Silicon isotope separation from hexafluorodisilane (Si 2 F 6 ) has been examined using a CO 2 pulsed laser. Si 2 F 6 containing certain isotopes was preferentially decomposed to SiF 4 depending on the wavenumber (k) of the laser. 2 9 Si and 3 0 Si were concentrated in the SiF 4 produced at k=945-955 cm - 1 , and in the residual Si 2 F 6 at k=970-980 cm - 1 . The SiF 4 containing 3 0 Si of about 43.3% and 2 9 Si at a maximum of 12.3% was continuously produced with a yield of 4.4% at k=951.203 cm - 1 and 9.6% at 956.205 cm - 1 , respectively. The decomposition reaction of Si 2 F 6 by the infrared laser irradiation could be explained as Si 2 F 6 (gas)+nhν->SiF 4 (gas)+SiF 2 (solid), calculated from a mass balance analysis of the experimental results. A 3 0 Si concentration higher than 90% was estimated to be achievable by repeating the irradiation of the residual Si 2 F 6 at around k=975 cm - 1 and finally decomposing the Si 2 F 6 to SiF 4 at k=951.203 cm - 1 . SiC enriched with 2 9 Si and 3 0 Si was predicted to show an excellent low activation behavior in fusion neutron environments.