1. An MPEG2 moving picture encoder to encode a video signal with digital watermark information and including a frame memory, a frame/field memory, an activity calculator, a rate controller, a Discrete Cosine Transform (DCT) unit, a quantizer, a dequantizer, an Inverse Discrete Cosine Transform (IDCT) unit, an adaptive estimator, a motion estimator, a variable length coder and multiplexer (VLC & a MUX) and a buffer, the MPEG2 moving picture encoder comprising: a digital watermark inserter installed between said DCT and said VLC & MUX, to generate and discrete-cosine-transform the digital watermark information, and then embed the digital watermark information on a frequency domain of the video signal; and a digital watermark remover, installed between said dequantizer and said IDCT, to remove the digital watermark information on a spatial domain of the video signal, so as to prevent an error during estimating motion on a temporal domain for P and B pictures of the video signal.