It is one objective of the present invention to provide a private branch exchange that can identify calls to be routed to an extension phone group.A private branch exchange according to this invention comprises: a caller information detector for, when a call is received, obtaining caller information; a group incoming call table in which two or more extension numbers are correlated with an extension incoming call group number; and an incoming call group controller for, when a call received through the telephone line is for an extension incoming call group number, extracting from the group incoming call table extension numbers that are correlated with the extension incoming call group number and transmitting an incoming call signal to extension phones corresponding to the extension numbers, and also for storing, in a group incoming call log table, a caller number that is obtained by the caller information detector.