An external index detection unit (105) receives an image sensed by a camera (100), and detects an external index set in a real scene. A tachometer (110) measures the rotational velocities of two rear wheels of a vehicle. A vehicle measurement unit (120) measures the position and azimuth of the vehicle on the basis of the image coordinate position of the external index and the rotational velocities of the two rear wheels of the vehicle. A head index detection unit (135) receives an image sensed by a camera (130), and detects a head index set on the head of a passenger (132). A head measurement unit (140) measures the position of the head on the basis of the image coordinate position of the head index. An image generation unit (150) generates a display image based on the position and azimuth of the vehicle and the position of the head, so that the passenger can observe predetermined navigation information superimposed at a predetermined position of the real scene, and controls a projector (160) to project the generated image.