A safety cabinet can adapt to variations in body height of a worker or user. The safety cabinet prevents various bacteria from proceeding from the outside of the safety cabinet into a working space of the safety cabinet and prevents bacteria or viruses from proceeding from the working space to the outside of the safety cabinet irrespective of a change in opening area of a front opening. A flow velocity of clean air supplied into the working space and a flow velocity of the air flowing through the front opening are set in accordance with a size of the front opening to maintain physical isolation and prevent contamination. The size of the front opening of the safety cabinet is adjustable.