An image information reading apparatus that can obtain high quality images without an effect of noise and a photographing condition or the like is realized even in the case where a low-bit A/D converter is used. The apparatus comprises control means for switching between pre-reading to main reading, characteristic determination means for determining, by analyzing an electric signal obtained by the pre-reading, a normalization processing characteristic used in normalization processing on an electric signal obtained by the main reading, and normalization processing means for carrying out the normalization processing on the electric signal in the main reading according to the determined normalization processing characteristic. The characteristic determination means analyzes image data by using a cumulative histogram of pre-reading data, and determines the normalization processing characteristic so that an image represented by the image data has adequate density and contrast.