1. An image processing apparatus comprising: a detection unit configured to detect a region of a subject from an input image; an extraction unit configured to extract an image feature amount from the region; a classification unit configured to classify the subject into any one of plural attributes based on the image feature amount; and an estimation unit configured to estimate, based on the image feature amount and an attribute into which said classification unit classifies, an attribute value of the subject belonging to the attribute into which said classification unit classifies.