1. An image processing apparatus comprising: an image acquiring unit which acquires photographed images, with photography ranges thereof being gradually changed; a commodity specifying unit which specifies a commodity and a position of the commodity based on the photographed images; a commodity map generator which generates a commodity map from the photographed images, based on the commodity and commodity position specified by the commodity specifying unit; and a commodity determination unit which generates a commodity inspection map representing differences between the commodity and commodity position shown in the commodity map and those shown in commodity layout plan information representing a commodity layout plan.