1. An image encoding method in which when transmitting or storing an image, a frame of the image is divided into predetermined-sized processing regions, and for each processing region, a pixel value of each pixel is predicted for the encoding, wherein the method comprising: an object number determination step that determines an object number that indicates the number of objects present in the processing region; an object pixel value determination step that determines one pixel value, which is assigned to and represents each individual object in the processing region, to be an object pixel value that is associated with an object identifier for identifying the relevant object; an object map generation step that generates, based on each object pixel value and the pixel value of each pixel in the processing region, an object map that indicates which object has been obtained at each pixel in the processing region, by using the object identifier; a predicted image generation step that generates a predicted image for the processing region by assigning the object pixel value to each pixel in accordance with the object map; an object map encoding step that encodes the object map; an object pixel value encoding step that encodes each object pixel value; and an image signal encoding step that performs predictive encoding of an image signal for the processing region by using the predicted image.