An input-output apparatus which is used in a process control system is provided. The input-output apparatus includes a first interface to which a lower-level apparatus is connected; a second interface to which a higher-level apparatus is connected; a third interface to which an external setting apparatus is connected; a switcher which switches between a connection of the second interface to the first interface and a connection of the third interface to the first interface; and a control device which, when in a first state in which the second interface is connected to the first interface by the switcher and the connection of the third interface to the first interface is permitted, controls the switcher to cause transitioning to a second state in which the third interface and the first interface are connected when a connection request to the first interface is input through the third interface.