The EFEM comprises: a transfer chamber in which a transfer robot is disposed, a first fan that forms a downward air flow in the transfer chamber, a gas return space that circulates the gas flowing downward in the transfer chamber above the first fan, a box that communicates with the transfer chamber and is provided with a gas outlet, and a connecting and disconnecting means configured to switch connection and disconnection of the box to and from the transport chamber. A circulation path in which gas circulates is formed by the transfer chamber, the gas return space, and the box. When the transfer chamber and the box are separated by the connecting and disconnecting means, a shortened circulation path is formed in which the gas circulates without passing through the box.