PROBLEM TO BE SOLVED: To safely sterilize an object containing bacteria by using nitrogen oxide.SOLUTION: A sterilization method includes: keeping an accommodation cavity (2) where an object (1) is placed in a hermetic state depressurizing the accommodation cavity (2) by using a depressurization device (3) introducing liquid nitrogen oxide from a reservoir tank (4) for reserving the liquid nitrogen oxide into the accommodation cavity (2) that has been depressurized or vacuumed, and gasifying the nitrogen oxide and sterilizing the object (1) by using the nitrogen oxide.
