An image processing apparatus includes a histogram computing section which computes a histogram of pixel values of input image data. A gradation conversion characteristic determining section determines a gradation conversion characteristic in a case where gradation conversion processing is applied to the image data on the basis of the histogram computed by the histogram computing section, and photographing information when the image data has been picked up. A gradation converting section converts the gradation of the input image data on the basis of the gradation conversion characteristic determined by the gradation conversion characteristic determining section.