To provide a multicast system capable of establishing a multicast tree rapidly so that a distribution delay stays within a predefined delay amount when new node addition or restructure of the multicast tree is required.

This multicast system is equipped with means for calculating in advance a predictive delay amount in the case of connection of an additional node for each node possibly serving as a connection destination before installing the additional node in a multicast tree having multiple nodes, means for storing the calculated predictive delay amount, and means for determining a node to which the additional node is connected using the predictive delay amount when installing the additional node.