To simply give information on inexpensive exchanging parts to a user when the expendable parts of each device connected to a network is exchanged.

A server terminal device 80 manages the expendable parts and operating situation of each device 82 connected to the network 83, and specifies the device 82 being the object of a retrieval request in response to the retrieval request given from a client terminal device 81 to the server terminal device 80. The server terminal device 80 obtains the consuming situation of the expendables predicted from the operating situation of the specified device 82 and selects the most inexpensive exchanging part from among the obtained expendables. The server terminal device 80 transmits information concerning the selected exchanging part to the client terminal 81, which displays the exchanging part on a display 96 in the increasing order of a cost.