1. An image processing apparatus comprising: a face detector configured to detect face images included in still-image frames successively extracted from a moving-image stream in accordance with image information items regarding the still-image frames; a face-feature-value calculation unit configured to calculate face feature values of the face images in accordance with image information items regarding the face images detected by the face detector; an identity determination unit configured to determine whether a first face image which is included in a current frame and which is detected by the face detector and a second face image which is included in a previous frame and which has been detected and stored by the face detector represent an identical person in accordance with at least face feature values of the first and second face images calculated by the face- feature-value calculation unit; and a merging processor configured to store only one of the first and second face images when the identity determination unit determined that the first face image and the second face image represent an identical person, and to store both the first and second face images when the identity determination unit determined that the first face image and the second face image do not represent an identical person.