An isolator includes a workroom having a first sterilizing material supply port, a first sterilizing material discharge port, a first gas supply port and a first gas discharge port, a sterilization chamber having a second sterilizing material supply port, a second sterilizing material discharge port, a second gas supply port and a second gas discharge port, a sterilizing material supply unit, a first sterilizing material supply path connecting the sterilizing material supply unit to the first sterilizing material supply port, a second sterilizing material supply path connecting the sterilizing material supply unit to the second sterilizing material supply port, a first circulating path connecting the first sterilizing material discharge port to the sterilizing material supply unit, a second circulating path connecting the second sterilizing material discharge port to the sterilizing material supply unit, a first gas supply path, a second gas supply path, a first gas discharge path, a second gas discharge path, and a control unit.