An isolator includes a work chamber, a sterilizing substance supply unit, a gas flow channel pressure adjustment unit, a work chamber barometer, and a controller. The controller is configured to control execution of a gas flow channel leak test for checking a gas leak in a gas flow channel based on a detection result by the work chamber barometer after making the gas flow channel pressure adjustment unit increase or decrease the pressure in the gas flow channel, and is configured to control supply of the sterilizing substance by the sterilizing substance supply unit. The controller performs heating of a heater, which accompanies the supply of the sterilizing substance, in parallel with the gas flow channel leak test.