PURPOSE: To attain response with priority from an incoming call having high emergency by providing a means in which an extension applying pickup operation responds to an incoming call calling an extension in the same group based on the priority provided in advance in response to the kind of call.

CONSTITUTION: If no incoming call to an extension E7 exists from a trunk COL, when an extension E8 tries pickup operation, a central controller CC confirms a belonging extension group G2 of the extension E8 and references a storage area M31 corresponding to a trunk line call having the highest priority and the connection relating to the trunk line call is not detected from a storage area M31, a storage area M32 corresponding to a relay line call having the 2nd priority is referenced to identify the presence of the connection. Moreover, the corresponding storage area M16 is referenced and it is identified that the extension E8 belongs to the same extension group G2 as the extension E8, the relay line PVL calling the extension E6 is connected to the extension E8 based on the process of pickup processing to allow the extension E8 to respond to the relay line PVL.