A communication relay device adds information to communication data without depending on a communication application of a communication terminal. The relay device (1) includes a relay control portion (13), a control information database (14), an adder portion (15) and a database for addition (16). The relay control portion (13) controls the adder portion (15) in accordance with information accumulated in the control information DB 14. The adder portion (15) adds the additional data accumulated in the database for addition (16) to decoded first contents in accordance with a control instruction by the relay control portion (13).