To efficiently reduce a redundant field even from a telecine picture that is converted not only by a 2:3 pull-down system but also by a linear interpolation type interpolation system.

A picture mixer circuit 6 obtains a synthesis picture of pictures of two past and future in-phase filed adjacent to a picture of a check object field ffm2 to discriminate whether or not a field is a redundant field. Whether or not the check object field ffm2 is a redundant field is discriminated on the basis of the correlation between the synthesis picture and the picture of the check object field ffm2. Thus, a mixture field by the linear interpolation type interpolation system whose discrimination has so far been difficult can be eliminated so as to reduce a data quantity of the coded picture data. Moreover, this method can be applied to even a telecine picture obtained by the 2:3 pull- down system by selecting a mixture ratio to the future in-phase filed to be zero.