1. An image processing apparatus that retrieves a specific image including a specific object area from a plurality of images, comprising: a storage unit configured to store management information of each of the images; a determination unit configured to determine whether or not object search information exists in the management information; a first processing unit configured to, in a case where said determination unit determines that the object search information does not exist, refer to an object dictionary in which feature value data items of objects are registered, and compare a feature value data item of an object detected from an image and the feature value data items of the object dictionary to thereby retrieve candidate images as candidates of the specific image; and a second processing unit configured to, in a case where said determination unit determines that the object search information exists, retrieve the candidate images based on the object search information.