Decontamination device and method for sterilizing an inside of facility or an inside of a device installed in the facility in which cells, tissues, culture media, sterile reagents, microorganisms or the like are handled or cultured, including: dry fog generating machine, installed in decontamination area, for converting peracetic acid mixed solution containing low-concentration peracetic acid into dry fog and spraying the dry fog into the decontamination area； humidity sensor, installed in decontamination area, for measuring humidity in decontamination area； gas recovery machine, installed in the above decontamination area, for recovering gas in decontamination area； and control device for controlling spraying from dry fog generating machine and gas recovery operation by the gas recovery machine based on information from the above humidity sensor, a main control and monitoring device, installed outside the above decontamination area, for controlling the control devices of one or more of the above decontamination devices.
