When saturation conversion is done by multiplying data by a saturation conversion parameter with a constant value regardless of image features, an image which can give good impression to the user cannot always be obtained. In this invention, an image is segmented into a predetermined number of blocks, and attributes are discriminated in units of blocks. Conversion characteristics are calculated on the basis of saturation conversion parameters of an image, which are set in correspondence with the discrimination result, and saturation is converted based on the calculated characteristics. In this way, appropriate saturation correction can be achieved in correspondence with the image attribute.