A stream data processing apparatus creates a plurality of partition data on the basis of stream data, and distributes the partition data to a plurality of computers. Specifically, the stream data processing apparatus acquires from the stream data a data element group that is configured in the number of data elements based on the processing capability of the partition data destination computer, and decides an auxiliary data part of this data element group based on a predetermined value. The stream data processing apparatus creates partition data that include the acquired data element group and END data. The data element group is configured from the auxiliary data part and a result usage data part.