PROBLEM TO BE SOLVED: To provide a device and a method for efficiently decontaminating a device for use in cell culture.SOLUTION: The present invention provides a decontamination device for decontaminating a device for use in cell culture, the operation of microorganisms or aseptic test, the decontamination device having an ultrasonic atomizer that atomizes a peracetic acid sterilization agent by ultrasonic vibration to release droplets, a diffusion fan, a temperature and humidity sensor, and a controller.SELECTED DRAWING: None