PURPOSE: To eliminate the deterioration in picture quality due to time shift as to the dynamic part of a picture, by using an interpolating signal by means of the pre-field interpolating method for a still picture part and using an interpolation signal by means of the average value interpolating method for the dynamic picture.

CONSTITUTION: When a subtraction output between a video signal Si and a signal one frame before is higher than a threshold voltage Vth, a high "1" signal is obtained at a terminal 30B. On the other hand, a subtraction output between the video signal Si and the signal before one frame is lower than the threshold voltage Vth, a low level "0" signal is obtained at the terminal 30. A terminal 29c is connected to a terminal 29a of a changeover switch 29, when a signal obtained at the terminal 30B goes to a low level "0", and the terminal 29c is connected to a terminal 29b when this signal goes to a high level "1". A video signal SNI' where the interpolating signal is formed with the pre-field interpolating method is obtained at a movable terminal 29c of the changeover switch 29 for the still picture part and a video signal SN being a video signal SNI" where the interpolation signal is formed with the average value interpolation method is obtained for the still picture part.