PURPOSE: To surely cancel an incoming call by sending a stored incoming packet to a terminal equipment and sending an interrupt instruction packet when the interrupt instruction packet is received after a setup procedure is finished.

CONSTITUTION: Upon the receipt of an incoming call packet CN through a network side line control section 4, a packet processing section 3 stores the CN to an incoming call packet storage section 6 and informs the arrival of the CN to an ISDN call processing section 2. The processing section 2 sends a setup message to a terminal equipment via a terminal line control section 5. When an interrupt command packet CI commanding cancel of an incoming call is received just after the processing, the CN stored in the storage section 6 is released and the incoming call cancelling is noticed to the processing section 2. The processing section 2 receives a RELEASE message from the terminal equipment accordingly and the cancellation is finished. Thus, it is possible to make incoming call cancellation in a short time and the operation of the terminal equipment after the incoming call cancellation is made stable and a succeeding call is surely replied.