An isolator for cultivating cells including a working chamber having a plurality of gloves arranged side by side into which operator's hands are inserted to operate cells, the working chamber being sectioned into at least an operation area for operating the cells, and an auxiliary working area for opening a packaged auxiliary instrument used to operate the cells, a gas supply unit that supplies gas into the working chamber so that the gas flows downwardly from an upper side in the working chamber, and a gas flow control unit for controlling the flow of the downwardly flowing gas so that the gas flows from the operation area to the auxiliary working area around the gloves, wherein the gas flow control unit has an exhaust hole portion that has an opened area for passing the gas therethrough and is provided at a lower portion of at least the auxiliary working area, and through which the gas in the auxiliary working area is exhausted.