A processing apparatus includes a distance image acquirer, a moving-object detector, a background recognizer. The distance image acquirer acquires a distance image containing distance information of each pixel. The moving-object detector detects a moving object from the distance image. The background recognizer generates a background model in which a stationary object recognized as background of the moving object is modeled, from the distance image acquired by the distance image acquirer. The moving-object detector changes a method for detecting the moving object, based on a relative positional relation between the moving object and the background model.