PROBLEM TO BE SOLVED: To improve a function of preventing a risk of gas leakage caused by failure in a locking means.SOLUTION: The gas sterilizing apparatus includes: a sterilizing chamber 3 having an opening 9 and a door to take in/out an object to be sterilized a door opening/closing mechanism 10 for retaining the closed state of the door 2 or releasing the retained state and a control means 8 for performing sterilization work by sterilizing the object to be sterilized within the sterilizing chamber 3 with a sterilization gas. In the gas sterilizing apparatus, the control means 8 puts an electric locking means 12 of the door opening/closing mechanism 10 at a locking position during the sterilization work, and the actuation of the electric locking means 12 is confirmed by a lock sensor 13 by temporarily putting the electric locking means 12 at a non-locking position before the start of the sterilization work and during the sterilization work.
