A calculating unit of an integration server calculates an optimal processing sharing ratio for image format conversion processing between the integration server and each of a plurality of video accumulation servers. A processing unit of the integration server and each of the video accumulation servers perform image format conversion processing in a distributed manner based on the processing sharing ratio. An integrating unit of the integration server integrates the multimedia data subjected to the conversion processing by each of the video accumulation servers and the multimedia data subjected to the conversion processing by the processing unit.