A video camera circuit for processing an image signal from an image pickup device having a mosaic color filter comprises a field memroy control circuit for reading out a predetermined line of signal (CCD output data) from a field memory when the position of vertical interpolation has changed, first, second and third line memories for storing the signal from the field memory, a line memory control circuit for controlling signal writing in and reading out from the line memories to concurrently retrieve three lines of signal, a vertical interpolation block for preparing a signal at the position of interpolation based on the four lines of signal, and a Y/C separation block for separating a luminance signal and color difference signals from the signal at the position of interpolation.