A multimodal service establishing method is provided which is capable of achieving flexible combinations of a plurality of service contents. At least one integrated server is installed between a plurality of terminal devices and service servers of a plurality of types. A session establishment processing unit and service linking processing unit are mounted in the integrated server. The session establishment processing unit establishes multimodal service session between terminals and service servers. After the establishment of multimodal service session, the service linking processing unit provides new service obtained by linking and integrating service to be provided by service servers, that is, multimodal service to terminal devices.