A message bus agent apparatus that is used as a first message bus agent apparatus in a system including a message bus management server, a signaling server, the first message bus agent apparatus, and a second message bus agent apparatus, the message bus agent apparatus including: signaling means that transmits, to the signaling server, a signaling message in which an agent ID of the second message bus agent apparatus issued from the message bus management server is designated as a connection destination; and connection means that establishes a connection with the second message bus agent apparatus as a virtual message bus based on processing of a signaling message by the signaling server.