In a method for controlling ISDN terminals connected to a passive bus conforming to an ISDN basic interface, the ISDN terminals being coupled to each other via a network, there are provided the following steps. A first step is to manage status of use of information channels in the passive bus by means of a communication server connected to the network. A second step is to send the communication server command data showing that the ISDN terminals will use the communication channels. A third step is to update management data showing the status of use of the information channels managed by the first step in response to receipt of the command data. A fourth step is to send updated management data showing the status of use of the information channels obtained after the command data is received to the ISDN terminals via the network.