PURPOSE: To prevent loss of business opportunity in advance by establishing a telephone set between a caller for an overflow call and a free dial contract party so as to realize much more communication without loss of communication.

CONSTITUTION: A caller telephone number of an overflow call not connected is delivered to a storage device 30, in which the telephone number is tentatively stored. A caller telephone number of an overflow call is sent from the storage device 30 to a telephone dialer 34 via a data line 32. The telephone dialer 34 processes dialing according to the overflow caller telephone number received from the storage device 30. The telephone dialing is executed by using a caller telephone line 36. As a result of dialing, when a line with an opposite party is connected, a channel between the telephone line 36 and a telephone set 38 is connected by a switching function incorporated in the telephone dialer 34 to attain the talking between the caller of the overflow call and an out-bound operator. While monitoring the talking state of the operator, the telephone dialer 34 implements dial processing.