A digital video signal processing apparatus and method for frame-based adaptive spatio-temporal Y/C separation. In the digital video signal processing apparatus, an adaptive three-dimensional bandpass filter (3D BPF) performs Y/C separation using local comb filtering/1D band pass filtering/frame comb filtering when the edge direction is fixed vertically/horizontally/temporally according to spatio-temporal local characteristics of an image using spatio-temporal filters. When the edge direction is not fixed horizontally/vertically/temporally, the 3D BPF performs 2D or 3D band pass filtering in all directions. Thus, the 3D BPF continuously carries out comb filtering, 1D band pass filtering, frame comb filtering and 2D/3D band pass filtering according to the spatio-temporal local characteristic of the image.