1. An image processing apparatus comprising: a facial image detection unit which detects a facial image from an input image; a posture estimation unit which estimates a posture of a person in the input image from a position of the facial image detected by the facial image detection unit; a hand position detection unit which detects positions of hands of the person based on the posture estimated by the posture estimation unit; a hand image extraction unit which extracts a hand image of the person from the input image based on information regarding the positions of the hands of the person detected by the hand position detection unit; a hand shape specifying unit which specifies shapes of the hands of the person based on the hand image extracted by the hand image extraction unit; a hand shape time-series storage unit which stores the shapes of the hands specified by the hand shape specifying unit in a time-series by corresponding to the information regarding the positions of the hands; and a hand gesture recognition unit which recognizes a hand gesture, which is a gesture using the hands of the person, based on information regarding the shapes of the hands stored in the time-series in the hand shape time-series storage unit by corresponding to the information regarding the positions of the hands.