An unauthorized apparatus detection device detecting clones of a playback device. In a management server, a reception processing unit acquires a user terminal identifier and a first random number of a user terminal, judges whether a second management server random number, which is stored in a storage unit in correspondence with the user terminal identifier, matches the first user terminal random number. If the two fail to match, a display unit displays a message indicating that a clone exists. If the two match, a terminal information generation unit generates a new random number, and writes the generated random number as the second random number in the storage unit. A transmission processing unit transmits the generated random number to the user terminal via a transmission/reception unit and the user terminal updates the first user terminal random number to the generated random number.