To provide the illegal data detection method where an inexpensive single memory with a large capacity is employed and falsification is difficult and to provide the pay broadcast receiver using the method.

The receiver is provided with a single body memory 520 that stores data and with an error detection information memory 550 that is hardly accessed from an external device in comparison with the single body memory 520. The error detection information memory 550 is accessible only via a memory control section 510. The error detection information memory 550 stores an error check code with respect to part of data or the data. An error detection section 540 compares storage contents of the error detection information memory 550 with storage contents of the single body memory 520 or uses data of the single body memory 520 and the error check code of the error detection information memory 550 to detect illegal falsification of the single body memory 520.