A method for judging delivery status of a push signal includes: receiving packets flowing in a specific session between a transmission source and transmission destination at an arbitrary point on a route of the specific session, and storing the received packets into a storage device, wherein the packets include voice packets and non-voice packets representing the push signal; judging based on sequence numbers included in the received packets stored in the storage device, whether or not packet loss has occurred in the specific session; and upon detecting that the packet loss has occurred, judging, according to status of the packet loss and predetermined characteristic of the non-voice packets, whether or not loss of the push signal has occurred.