Stream data is structured including data tuples as a query process target and a recovery point tuple for indicating a position of the data tuples in the stream data. Upon detection of a failure at a computer, another computer reads position information in the stream data indicating a position of data tuples already subjected to the query process by a stream processing apparatus from a recovery points, uses the recovery point positioned lastly among the read recovery points as a reenter point of the input stream, and instructs a stream distribution apparatus to reenter the input stream starting from the reenter position into the other computer.