PURPOSE: To prevent a video signal at the standard speed from being affected with change in speed by changing the ratio of an effective horizontal scanning region period to a horizontal blanking period in a TV camera having a higher scanning speed and restoring the ratio to the initial value at the speed conversion.

CONSTITUTION: The scanning speed of a television camera 21 is N times the standard scanning speed and the ratio of the effective horizontal scanning region period to the horizontal blanking period is set smaller than that of the standard scanning speed, i.e., the horizontal blanking period is set wider. An output of the camera 21 is fed to an A/D converter 23 via an LPF23 and converted in a high speed sampling rate. Then the output of the A/D converter 23 is fed to a speed converting circuit 24 and the time ratio of the effective horizontal scanning region period to the horizontal blanking period is restored to the normal ratio. No effect is exerted on the video signal in the standard speed in such a way.