A game apparatus detects a predetermined image object including a first graphic pattern with a plurality of inner graphic patterns drawn therein from a captured image captured by an image-capturing section. The game apparatus first obtains the captured image captured by the image-capturing section, and detects an area of the first graphic pattern from the captured image. Then, the game apparatus detects the plurality of inner graphic patterns from within the detected area, and calculates center positions of the inner graphic patterns so as to detect the position of the predetermined image object.