1. An image processing apparatus comprising: a image input unit adapted to input a image; a partial region extraction unit adapted to extract a partial region from the image; a feature amount extraction unit adapted to extract a feature amount of the extracted partial region; a first determination unit adapted to determine a similarity between the extracted feature amount and a feature amount of a partial region of a registered image which is registered in advance in a database; a first setting unit adapted to set a region in the image based on the registered image corresponding to the partial region which is determined by said first determination unit to have a high similarity; and a second determination unit adapted to determine a similarity between a feature amount of the region set by said first setting unit and the feature amount of the registered image.