To efficiently decomposing ozone gas and drying an object in a circulation type sterilizing apparatus.

The sterilizing apparatus 1 includes: a sterilizing chamber 2 for holding the object 9 and sterilizing the object 9 with a treatment gas containing the ozone gas inside the chamber; a fan 32 for circulating the treatment gas in a circulation flow passage 31 from an exhaust port 221 to an intake port 211 in the sterilizing chamber 2; and an ozone gas decomposition unit 5 arranged in the circulation flow passage 31. The ozone gas decomposition unit 5 includes a first ozone gas decomposing part for heating the treatment gas circulating in the circulation flow passage 31 after the sterilization of the object 9, and then, thermally decomposing the ozone gas in the treatment gas. When the ozone gas is decomposed after the sterilization of the object 9 in the sterilizing apparatus 1, the treatment gas is heated by a heater, the ozone gas is thermally decomposed, and also the object 9 inside the sterilizing chamber 2 is dried with the use of the heated treatment gas. Thus, the decomposition of the ozone gas and the drying of the object 9 are efficiently performed.