1. A method of detecting a skin-colored area using a variable skin color model, comprising: a first stage of extracting an initial skin-colored area from an input image using a skin color model, wherein the initial skin-colored area being repeatedly extracted by adjusting a threshold value, which is a criterion for selection of a skin-colored area, until a ratio of a size of the extracted initial skin-colored area to a size of the entire input image becomes less than a predetermined value; and a second stage of extracting a skin-colored area by applying the threshold value determined in the first stage to the skin color model, the skin color model being modified by analyzing characteristics of object regions and noise regions of the skin-colored area; wherein the second stage comprises: a first step of extracting the skin-colored area by applying the threshold value, determined in the first stage, to the skin color model; a second step of dividing the skin-colored area extracted at the first step into object regions and noise regions, and analyzing characteristics of the object regions and the noise regions; a third step of determining whether the number of object regions starts to be at a constant level, thus determining whether a desired skin-colored area has been extracted; a fourth step of modifying the skin color model and repeating a procedure starting from the first step if it is determined that the number of object regions is not at the constant level; and a fifth step of outputting results of the extraction of the skin-colored area if it is determined that the number of object regions is at the constant level, wherein at the fourth step, the skin color model is modified based on a color value of a pixel included in the object regions and a color value of a pixel included in the noise regions.