1. An image processing apparatus for extracting one or a plurality of objects, in the case where a plurality of stationary objects and a plurality of moving objects are contained together as a group of objects in one image, comprising: an image-input unit ( 1 ) which inputs an image including a background and a plurality of said objects; a background image extract unit ( 2 ) which extracts and stores said background; a first average background extract unit ( 3 ) which extracts an image that includes one or a plurality of said stationary objects or moving objects each having a speed not higher than a predetermined first speed and also includes said background; a second average background extract unit ( 4 ) which extracts an image that includes one or a plurality of said stationary objects or moving objects each having a speed not higher than a predetermined second speed and also includes said background; a first difference-calculation processing unit ( 5 ) which calculates a difference value between an output from said background image extract unit ( 2 ) and either one of outputs from said first average background extract unit ( 3 ), and then generates a first speed image; a second difference-calculation processing unit ( 6 ) which calculates a difference value between respective outputs from said first and second average background extract unit ( 3, 4 ), and then generates a second speed image; and a third difference-calculation processing unit ( 7 ) which calculates a difference value between an output from said image-input unit ( 1 ) and either one of outputs from said first and second average background extract unit ( 3, 4 ), and then generates a third speed image.