1. An image processing apparatus comprising: a face detection unit which detects faces from an input image; an evaluation value calculation unit which calculates an evaluation value expressing a degree of a facial expression for each of the facial expressions of the faces detected by the face detection unit; and a control unit which changes a standard for extracting an image such that an image including the facial expressions, that a small number of people have, is easily extracted, based on the number of people for each of the facial expressions of the faces detected by the face detection unit and an evaluation value for each facial expression of the face calculated by the evaluation value calculation unit.