To provide a call data processing system for processing the call data of one data communication(one speech) at a single place even when one data communication is operated across a plurality of switchboards by introducing a protocol converting device.

A protocol converting device 40 is interposed between line networks with different protocols connected through a plurality of switchboards 112 and 113, and data communication between terminal devices connected with the line networks with different protocols, respectively, is performed in this data communication system. This system is provided with a call data assembly processing means (calling data collecting device) 10 for operating the assembly processing of call data (first calling data) related with the line network having a certain protocol and call data (second call data) having another protocol.