A communication system comprising: a communication control apparatus; and a plurality of communication devices, each communication device being configured to operate a secondary system of a plurality of secondary systems using a spectrum assigned to a primary system, wherein each communication device comprises: a control unit configured to: receive, from the communication control apparatus, a list of channels, and select, for the secondary system, a channel from among the list of channels, wherein the communication control apparatus is configured to: acquire information about channels, among frequency channels assigned to the primary system, available to the secondary system of the plurality of secondary systems from a server, acquire information about the secondary systems from the communication devices, generate the list of channels from the available channels recommended for each communication device based on the information of the secondary systems, and decide the channels recommended to the communication device in such a way that the total of interference with the primary system caused by secondary systems does not exceed the permissible amount of interference of the primary system. a communication control apparatus; and a plurality of communication devices, each communication device being configured to operate a secondary system of a plurality of secondary systems using a spectrum assigned to a primary system, wherein each communication device comprises: a control unit configured to: receive, from the communication control apparatus, a list of channels, and select, for the secondary system, a channel from among the list of channels, wherein the communication control apparatus is configured to: acquire information about channels, among frequency channels assigned to the primary system, available to the secondary system of the plurality of secondary systems from a server, acquire information about the secondary systems from the communication devices, generate the list of channels from the available channels recommended for each communication device based on the information of the secondary systems, and decide the channels recommended to the communication device in such a way that the total of interference with the primary system caused by secondary systems does not exceed the permissible amount of interference of the primary system. a control unit configured to: receive, from the communication control apparatus, a list of channels, and select, for the secondary system, a channel from among the list of channels, receive, from the communication control apparatus, a list of channels, and select, for the secondary system, a channel from among the list of channels, wherein the communication control apparatus is configured to: acquire information about channels, among frequency channels assigned to the primary system, available to the secondary system of the plurality of secondary systems from a server, acquire information about the secondary systems from the communication devices, generate the list of channels from the available channels recommended for each communication device based on the information of the secondary systems, and decide the channels recommended to the communication device in such a way that the total of interference with the primary system caused by secondary systems does not exceed the permissible amount of interference of the primary system. acquire information about channels, among frequency channels assigned to the primary system, available to the secondary system of the plurality of secondary systems from a server, acquire information about the secondary systems from the communication devices, generate the list of channels from the available channels recommended for each communication device based on the information of the secondary systems, and decide the channels recommended to the communication device in such a way that the total of interference with the primary system caused by secondary systems does not exceed the permissible amount of interference of the primary system.