Provided is a safety cabinet configured so that a work room can be decontaminated by circulating ozone gas within the work room while the leakage of the ozone gas from the work room during the decontamination can be prevented. A safety cabinet is provided with: a cabinet body (1) a shutter (4) capable of opening and closing an opening (3) in communication with a work room (2) a gas discharge passage (6) for discharging gas from the work room (2) a gas discharge valve (B2) provided in the gas discharge passage (6) a fan (P1) for supplying air and for circulation which is provided in the work room (2) an ozone generator (13) for introducing ozone gas into the work room (2) a control unit (10) for controlling the gas discharge valve (B2) the fan (P1) for supplying air and for circulation and the ozone generator (13) and a gastight closure means (30) capable of gas tightly closing the opening (3) by means of the shutter (4). Gas within the work room (2) can circulate therein and consequently the work room can be decontaminated on the basis of a set CT value by means of the ozone gas by circulating the ozone gas within the work room while the leakage of the ozone gas is prevented.
