PURPOSE: To utilize the service without dial operation and to surely deliver only a message by devising the system such that the message sent to a busy extension is stored and delivered automatically to the extension after the busy state is finished.

CONSTITUTION: When a call comes from a public line 9, or a relay line 11 or other extension telephone set C3 to a busy extension telephone set A1, a central processing unit 14 connects the call to a message input output controller 12 and sends a message representing a busy state notice and a message request to a caller from a message storage device 13 and stores the message from the caller. A line type of the incoming call and an extension number of the extension telephone set A1 are stored in a main storage device 15 simultaneously. When the busy state of the extension telephone set A1 is released, the central processing unit 14 calls the extension telephone set A1 and connects it to the message input output controller 12 when the telephone set A1 replies to send the caller message stored in the message storage device 13 to the telephone set A1.