PURPOSE: To provide the multiple communication method and device in which a processing efficiency can be improved, and the valid utilization of a CPU resource can be realized, at the time of connecting plural communication lines with the computer such as a personal computer or work station (PC(WS)).

CONSTITUTION: A multiple communication controller 6 which controls plural communication lines TL1-TL3 is connected with a PC(WS) 1, data and record transmitted and received by each communication line are condensed, and converted into a common record format and transferred, between the PC (WS) 1 and the multiple communication controller 6. Thus, the load and loss time of a CPU and an OS due to a communication control instruction and a waiting time generated at the time of simultaneously holding plural communication sessions by one PC(WS) 1 can be reduced, and the instruction processing efficiency of the system of the PC(WS) 1 can be improved.