A vehicular ECU (electronic control unit) is any one of a plurality of vehicular ECUs connected to an in-vehicle network in a vehicle and includes: a service interface, a service bus, and a service manager. The service interface issues a request of service that uses a function installed in a different vehicular ECU based on a request from the application, and makes the application generate a service as a response to a request of service from the different vehicular ECU. The service bus transmits and receives a message corresponding to a request of service and a response by using a predetermined protocol between the service interfaces of the vehicular ECU and the different vehicular ECU. The service manager achieves the service to be dynamically and interoperably used by managing a position of the service.