To determine an image type to perform proper gray scale correction, there are provided a gray scale histogram calculator (1) that calculates a gray scale histogram of gray scale components for each color component; a maximum/minimum calculator (3) that uses these gray scale histograms to calculate, for each color component, a maximum and a minimum of classes having a frequency greater than zero; an image type determiner (2) that generates, from adjacent classes and frequencies in the gray scale histograms, an absolute difference value histogram for each color component, compares the absolute difference values with a predetermined threshold value to determine, according to the presence or absence of an absolute difference value exceeding the threshold value, a size of an area of image regions where the gray scale components are uniform, and determines an image type; a gray scale correction curve generator that generates a gray scale correction curve for correcting a gray scale of an image signal for each color component so that a largest and a smallest of the maximum and minimum of the classes for each color component are set as a maximum and a minimum of the gray scale correction curve; and a gray scale corrector (5) that uses the gray scale correction curve to perform gray scale correction for each color component.