The time required to execute processing for detecting the image of a face is shortened. A number of frames of the image of a subject are obtained sequentially by sensing the image of the subject successively. Face detection processing is applied to a first subject image, which is one frame of the image of the subject among the number of frames thereof. The inclination of a face-image area obtained by detection is detected. Among angles of 0°, 90°, 180° and 270°, that close to the detected inclination is decided upon. A face image having an angle within a range of 45° on either side of the decided angle as its inclination is detected from a second subject image, which is obtained following the first subject image. Since face images to undergo detection are thus restricted, detection processing ends in a comparatively short period of time.