A monitoring apparatus holds extracted information including: extracted data from first communication between a proxy and a first network and from second communication between the proxy and a second network; and reception times of a target data, wherein the extracted data includes kinds of communication, sources and destinations of the target data in the first communication, and the sources in the second network and the destinations in the first network after the target data is relayed by the proxy in the second communication, the monitoring apparatus: for first extracted data of first kind of communication in the first communication, acquires second extracted data in the second communication whose reception time is coincidental time zone of the reception time of the first extracted data; and determines whether communication using the target data from which the acquired second extracted data is extracted is included in a series of end-to-end communication.