A customer submits a service application by accessing the home page of a service provider through a personal computer 3, and transmits the data including the operation amount and the control amount of a temperature controller 4 to a server 2 of the service provider. The server 2 accumulates the received data, and in accordance with the contents of the received service application, processes the accumulated data and provides the services of calculating the control parameter for the temperature controller 4, producing a model of the object of control and making a diagnosis by checking for a temperature control fault.