An EFEM includes a housing having a substantially closed substrate transfer space in the housing and a control part configured to perform a control of supplying an inert gas into at least the housing. The control part includes an inert gas total supply amount setting part configured to set a total supply amount of the inert gas to be supplied into the housing; a door open/purge determination part configured to determine whether a container door of a substrate storage container is in an open state and whether a purge device is performing a purge process; and an in-housing inert gas supply amount calculation part configured to calculate a supply amount of the inert gas to be supplied into the housing. The supply amount of the inert gas to be supplied into the housing is determined according to an inert gas supply amount command value determined based on a calculation result.