1. An object image detection device for detecting one or more object images from an input image, comprising: an image block generation unit configured to generate a plurality of image blocks from the input image for detecting the object images; an image classification unit configured to determine whether each of the image blocks includes one or more of the object images by using one or more features of the object images, and acquire the image blocks including the object images to be object image candidates; a detection unit configured to sequentially detect the object images from the object image candidates; a hierarchical image structure generation unit configured to arrange the input image in a hierarchical manner to generate a hierarchical image structure of the input image; wherein the image block generation unit generates the plural image blocks from the input image on each layer of the hierarchical image structure, the image classification unit acquires the object image candidates on each of the layers of the hierarchical image structure; and wherein the image classification unit discards one or more of the image blocks in a current layer at least partially overlapping any of the already-acquired object image candidates in other layers from the current layer, and acquires the object image candidates of the current layer only from the remaining image blocks.