1. An apparatus for extracting an object comprising: an image receiver configured to receive an image; a coupled saliency-map generator configured to generate a coupled saliency-map which is the sum of the product of a global saliency-map of the image and a predetermined weight value and a local saliency-map, wherein the local saliency-map is a saliency-map including pixels representing Euclidean distance between a mean color vector of each pixel of the image and a vector generated through Gaussian blur treatment for the image, and wherein the global saliency-map is a saliency-map defined based on space and color of regions which are segmented to each component after representing the image in a Gaussian mixture model composed of a plurality of components; an adaptive tri-map generator configured to generate an adaptive tri-map corresponding to the coupled saliency-map, wherein the adaptive tri-map generator generates a tri-map from the coupled saliency-map through Gaussian blur and image clustering, selects a pixel, of which distance is the least to any one of mean color values of foreground region, background region and unknown region of the tri-map among pixels of the coupled saliency-map, as the shortest distance pixel, and generates the adaptive tri-map by replacing a pixel value of the tri-map, corresponding to the shortest distance pixel and a pixel adjacent to the shortest distance pixel, as a mean color value of the foreground region when the shortest distance pixel is identical to the mean color value of the foreground region and is located within the unknown region of the tri-map; an alpha matte generator configured to generate, using a preconditioned conjugate gradient method, an alpha matte based on the adaptive tri-map; and an object detector configured to extract an object according to transparency of the alpha matte to generate an object image.