Provided are moving picture encoding apparatus and method skipping intra prediction in encoding mode determination using rate-distortion (RD) costs and determining an encoding mode at high speed. The moving picture encoding method includes the steps of: setting the lowest one of rate-distortion costs of macroblocks adjacent to a macroblock to be encoded as a threshold value; setting the lowest one of mode-specific distortion costs obtained by inter prediction for the macroblock to be encoded as an optimum inter mode distortion cost; comparing the threshold value with the optimum inter mode distortion cost; and when the threshold value is larger than the optimum inter mode distortion cost, as a result of the comparison, skipping intra prediction and setting a mode having the optimum inter mode distortion cost as a final encoding mode.