In the present invention, the following are provided: a storage unit that sequentially stores messages received within a predetermined time period from an input interface which sequentially accepts messages output from a plurality of contexts; a message extraction unit that breaks down the messages stored in the storage unit into element messages, which are output units of a message that have been predetermined on an output side of the plurality of contexts; and a message reconstruction unit that selects element messages which match predetermined appearance patterns of the element messages to reconstruct a message.
