Provided is a sterile environment maintaining apparatus capable of sterilizing a sterile room in a shorter time than conventional ones.The sterile environment maintaining apparatus according to the present invention comprises a sterile room 10 having an inlet opening 11 and an outlet opening 12, a HEPA filter 3 placed so as to cover the inlet opening 11 or the inlet opening 11 and the outlet opening 12 of the sterile room 10, and a sterilizing material supplying part supplying a sterilizing material such as hydrogen peroxide to the sterile room 10, and the sterile room 10 is provided with a detoxifying material supplying part spraying a detoxifying material such as ozone toward the HEPA filter 3.