A method and an apparatus adaptively encode a motion image based on temporal and/or spatial complexity. In the method, encoding is performed with different temporal and spatial resolutions at frame rates based on the temporal and/or spatial complexity of an input image so that image data is stored with high efficiency. The method includes calculating a spatial complexity of input image data, determining a resolution by comparing the calculated spatial complexity with a predetermined threshold, and converting the resolution of the input image data based on the resolution.