The present invention relates to a gas sterilizer. The gas sterilizer has a shell, a disinfecting device, an ozone generator, a cleaning device and a driving device. The disinfecting device, the ozone generator and the cleaning device are mounted in the shell. The driving device drives outside air to flow through the ozone generator to produce ozone. The ozone is driven by the driving device and flows into the disinfecting device to perform sterilization functions. Then, the ozone in the disinfecting device is cleaned by the cleaning device and is exhausted. The gas sterilizer uses the ozone generator producing ozone and provides a simple way to sterilize a biomaterial and decreases the denaturation degree of the biomaterial and increases the applicability of the gas sterilizer.
