An apparatus for monitoring a multicast group is provided. The apparatus includes a storage, a receiver and an operation processor. The storage is configured to store first data including a first authenticated message authenticated as being published by a publisher of the multicast group to n-th data including an n-th authenticated message authenticated as being published by the publisher where n is a natural number of 2 or more. The receiver is configured to receive status data including a first propagation message to be delivered to the multicast group. Further, the operation processor is configured to generate monitoring information including status information of the multicast group by using the status data and the first to n-th data.