An apparatus for encoding a moving picture determines either an RGB format or a YUV format, in which intra prediction and inter prediction are executed based on a degree of deviation of information regarding each of R, G, and B components in moving picture data with the RGB format when a prediction selecting one component among three components in a color space format is designated in the input moving picture data with the RGB format, selects either color space format between the RGB format and the YUV format based on a determination result of the determination process, and executes orthogonal transform and quantization on the prediction error signal in the selected color space format and generating an encoded bit stream using a value subjected to the orthogonal transform and the quantization.