When an image representing biological information is input from a biological information input unit 10, such as a fingerprint sensor or the like, for obtaining an image representing biological information, such as a fingerprint or the like, statistical quantities, such as the mean value and standard deviation of the pixel values of the sampled image, are calculated. Then, using the statistical quantities, a region containing biological information is extracted, its sensitivity variations are eliminated and the effects of stains, such as a residual fingerprint is nullified, thereby generating a favorable biological image with high contrast.