1. An image surveillance/retrieval system comprising: an image input unit for receiving image data; an object processing unit for dividing each image frame of the image data into a plurality of block areas, for detecting each individual object from each image frame, for extracting, as one object, a series of appearances of each identical object in a plurality of image frames, and for extracting features of the object extracted as metadata for each of the plurality of block areas; a metadata storage unit for storing the metadata obtained by said object processing for each of the plurality of block areas; a query input unit for receiving a real-time detection query or a post-retrieval query; a real-time detection processing unit for comparing the metadata for each of the plurality of block areas with the real-time detection query received by said query input unit, and for detecting an object which satisfies the real-time detection query; a post-retrieval processing unit for comparing the metadata for each of the plurality of block areas which is stored in said metadata storage unit with the post-retrieval query received by said query input unit, and for retrieving an object which satisfies the post-retrieval query; and a display unit for displaying either the object detected by said real-time detection processing unit or the object retrieved by said post-retrieval processing unit.