To provide a three-dimensional Y/C separating circuit that has a high responsibility to a motion in a video signal and can reduce a memory capacity, a three-dimensional Y/C separating circuit has a 2-frame memory 14 that delays a color signal by an inversion period thereof to produce a delayed composite video signal, a luminance motion detecting part that produces a first frame correlation signal by a subtraction processing between the delayed composite video signal and a composite video signal, an adding circuit 23 that produces a mixed video signal by an addition processing between the delayed composite video signal and the composite video signal, a frame memory 24 that delays the mixed video signal by one frame period, a subtracting circuit 25 that produces a second frame correlation signal by a subtraction processing between the mixed video signal and the mixed video signal delayed by one frame period, a determining circuit 26 that determines a motion from the first and second frame correlation signals and produces a mixing ratio controlling signal, and mixing circuits that output a luminance signal and a color signal, respectively, based on the mixing ratio controlling signal.