A data stream inputted to the inventive system from the outside is supplied to a PID (packet ID) extracting circuit 1, in which a PID is detected from a transport stream TS regardless of whether the transport stream TS is a full transport stream TS or a partial transport stream TS. The PID extracting circuit 1 transmits the thus extracted PID and data stream to a TS replacing/deleting circuit 2. The TS replacing/deleting circuit 2 has n 188-byte buffers and is able to set replaced TS packets to the buffers. A control circuit 3 such as a CPU (central processing unit) designates m PIDs relative to the respective buffers and designates the respective PIDs as the PID of the packet to be deleted or the PID of the packet to be replaced. Then, the TS replacing/deleting circuit 2 compares the PID received from the PID extracting circuit 1 with the PID designated by the control circuit 3. If they are identical to each other, then the PID that is set to be replaced is replaced and the PID that is set to be deleted is deleted. Thus, the packet indicative of attribute of data can be replaced satisfactorily.