A method and apparatus for dithering for multi-toning are provided. The apparatus includes a mask-pattern-generating unit that generates a mask pattern on R channel, G channel and B channel by selecting pattern values constituting the mask pattern on the channels based on randomly-determined seed values; a spatial-weight-determining unit that determines the weight for spatial dithering by using the pattern values and K-bit LSB data of the high-tone input image; and an output unit that outputs an M-bit image by applying the weight to M-bit input image data, exempting the K-bit LSB data, in a dithering apparatus for expressing an M+K bit high-tone input image in an M-bit low-tone output device.