Abstract: A safety cabinet is capable of preventing ozone gas from leaking out of a working chamber during decontamination and circulating the ozone gas in the working chamber to decontaminate the working chamber. The safety cabinet includes a cabinet main body; a shutter that allows opening/closing of an opening part communicatively connecting to a working chamber; an exhaust path through which gas is exhausted from the working chamber; an exhaust valve that is provided in the exhaust path; an air supply and circulating fan that is provided in the working chamber; an ozone generator that introduces ozone gas into the working chamber; a control part that controls the exhaust valve; an air supply and circulating fan; and airtightly closing device that allows the shutter to airtightly close the opening part are included.