There is provided a scanning line interpolation device which is capable of providing an interpolated image with increased reproducibility of vertical high-frequency components in a still picture part. Preceding-field image data is stored in a field memory, and thereafter reference pixels which are located in an interpolation pixel position and its surrounding positions and required for interpolation are extracted from the preceding-field image data stored in the field memory and current-field image data. An inter-field motion judgement portion detects whether or not there is a motion of an image between preceding and current fields based on the extracted reference pixels. If the inter-field motion judgement portion detects that there is a motion, a selection circuit selects in-field interpolation data calculated in an in-field interpolation value calculation circuit from the current-field image data among the reference pixels. If the inter-field judgement portion detects that there is no motion, the selection circuit selects the preceding-field image data located in the interpolation pixel position among the reference pixels. Then, the selection circuit outputs the selected data as interpolation pixel image data.