A relay apparatus includes a reception processor configured to receive data corresponding to any one of plural types of communication protocols from a first network, analyze the structure of the received data, and convert information commonly included in the data of the communication protocol into common data of a predetermined format, a transmission processor configured to transmit data corresponding to any one of the plural types of communication protocols to a second network, and a relay controller configured to control the communication protocol and destination of the received data to be transmitted from the transmission processor to the second network, based on the common data and a relay rule which is defined for the common data.