PURPOSE: To obtain a ciphered broadcast equipment without losing the naturality of audible and visual sense by eliminating optimizingly a delay time caused between a sound signal and a video signal.

CONSTITUTION: The transmission side 11 is provided with a video ciphering circuit 12 and a sound ciphering circuit 13. The delay time of a delay circuit 14 is set to a sum between the processing time difference of the video and sound ciphering circuits 12, 13 and the processing time difference of the video and sound ciphering circuits 12, 13 at the reception side 16. A ciphered video signal and a ciphered sound signal are multiplexed by a multiplexing circuit 15 and irradiated as a radio wave. The radio wave is separated into the ciphered video signal and the ciphered sound signal at the receiving side 16 while being demodulated, they are applied respectively to a video decoding circuit 18 and a sound decoding circuit 19, where they are decoded. Thus, the time difference between the video signal and the sound signal at decoding is almost eliminated.