The present invention provides a network contents managing system on a network comprising: a contents database retaining locations and attributes of contents and data; a retrieval request detection unit for detecting a retrieval request to the contents database and outputting a retrieval request information; a network monitoring unit for monitoring a change of an apparatus connection state to the network and, upon occurrence of a change of the connection state, outputting a new apparatus connection state as a connection state information; a contents monitoring unit for outputting a contents modification information when a location and an attribute of contents and data is modified; a database retrieval unit for retrieving the contents database upon reception of the retrieval request information and outputting a retrieval result information; a database managing unit for performing registration and modification in the contents database upon reception of the connection state information and the contents modification information; and a retrieval result output unit for outputting the retrieval result information to the apparatus which has made the retrieval request. Thus, it is possible to dynamically grasp the client apparatus connection state and the contents modification.