An apparatus is disclosed which sterilizes vessels 4 carried by vessel holder means 14 and conveyed within an aseptic chamber 82 by irradiating the vessels with an electron beam from an electron beam irradiator 24. An injector 87 which injects H2O2 gas is disposed within the aseptic chamber 82 to maintain H2O2 gas atmosphere in the aseptic chamber 82. In this manner, a vessel sterilizer having a high reliability can be provided by avoiding the likelihood that germs which are introduced into the aseptic chamber 82 by being attached to the vessels 4 may be re-attached to the sterilized vessels 4 if the germs remain floating.
