1. A method of entropy encoding a plurality of current coefficients of a quality layer among a plurality of quality layers of an image block divided into the plurality of quality layers, the method comprising: determining a coding pass with respect to each of the current coefficients; selecting a context model with respect to each of the current coefficients using at least one lower coefficient corresponding to each of the current coefficients if the coding pass is a refinement pass; and encoding a group of coefficients having a same selected context model among the current coefficients using the selected context model.