The present invention discloses a method for fabricating silica glass using a sol-gel process, which includes a sol forming step for forming a sol by mixing a starting material, deionized water and an additive together; gelation step for gelatinizing the sol after filling a circular mold with the gel produced; gel drying step for separating the gel from the circular mold and drying the gel; setting step for placing the gel inside of a heat chamber and injecting helium gas into the heat chamber; and low heat treatment step for pressurizing and depressurizing an internal pressure of the heat chamber repeatedly for several times.