Provided is a method and apparatus for classifying geological materials using image processing techniques. The method and apparatus classify geological materials including stones, rock samples, and rock surfaces according to type and state by sequentially applying image processing techniques, such as a color space analysis, a granulometry analysis, texture parameter extraction and texture statistics extraction, to digital images of the geological materials. Since the method and apparatus extract quantitative figures that represent an entire image region by applying various image processing techniques, such as the color space analysis, the granulometry, the texture parameter extraction and the texture statistics extraction, to the digital images of the geological materials, the geological materials can be classified, which is not possible using a conventional image processing technique.