A safety cabinet has a second operation chamber in a first operation chamber and into which clean air is supplied, a second suction opening for sucking in air in the second operation chamber and a portion of the air in the first operation chamber, and a second operation opening part that is provided facing a first operation opening part and communicates the second operation chamber with the first operation chamber. Airflow containment (air barrier) is doubled with respect to the outside of a safety cabinet. In cases where decontamination and disinfection operations are carried out according to the changeover procedures, intensive decontamination and disinfection of the second operation chamber is sufficient, and decontamination and disinfection of the first operation chamber is hardly required. Decontamination and disinfection operations in the changeover procedures and the like can be carried out in a greatly reduced time.