To perform wide-angle photographing using one mirror without being affected by vignetting.

A camera unit 100 includes a camera 10 and a mirror 11, and the camera 10 is installed at the ceiling and disposed at a right angle to the mirror 11. The camera 10 then photographs an image in a state that a half of the image is inverted with respect to the other half of the image. The address control section 222 of a partial mirror image inverting section 220 controls addresses of a memory 221 so as to read camera images in the reverse order of addresses, only for left-half images, when reading the camera images from the memory 221. Thus, the image inverting section 220 inverts any half of the image photographed by the camera 10 and outputs a stereo image. A stereo image processing section 223 then detects an object (e.g., a human being) included in the stereo image from the partial mirror image inverting section 220 and outputs a detection result.