The surface tension of coal extracts fractions, i.e., acetone soluble (AS), and pyridine soluble-acetone insoluble (PS) fractions, in N-methyl-2-pyrrolidinone was measured at 25℃ by the Wilhelmy plate method. The surface tension was decreased as AS concentration increased and then its decrease rate became slow down at a certain concentration at which micelle-like coal associates may begin to form. The similar behavior has been reported for the solution of petroleum asphaltene in pyridine. On the other hand, the surface tension of PS, which is a heavier fraction than AS, showed no concentration dependence.