1. An image processing apparatus for making predetermined image sensing means sense a scene in a fixed image sensing direction, and extracting an object from an image obtained by the image sensing means, comprising: image input means for inputting frame images which are sensed by the image sensing means and are sequential in a time axis direction in turn; smoothing means for smoothing the input frame images; background image determination means for determining the smoothed frame image as a background image; differential image generation means for generating a differential image between a predetermined smoothed frame image and the background image; and object region extraction means for extracting an object region where a predetermined object is sensed, on the basis of the differential image.