PROBLEM TO BE SOLVED: To provide a method for reliably and safely decontaminating the interior of a safety cabinet and the interior of an operator room, with efficiently reduced time required for resuming normal operations after decontamination.SOLUTION: The decontamination method of a biohazard facility includes decontaminating the interior 3a of a safety cabinet 3 and an operator room 2 in which the safety cabinet 3 is disposed, by using decontamination gas. With the interior 3a of the safety cabinet 3 being sealed relative to the interior of the operator room 2, the interior 3a of the safety cabinet 3 is filled with formaldehyde gas as decontamination gas, and the interior of the operator room 2 is filled with hydrogen peroxide gas as decontamination gas, so that the interior 3a of the safety cabinet 3 and the operator room 2 are decontaminated at the same time.
