A compact buckle, streamlined in appearance, comprises a main body and a stopper piece. The main body includes a pair of side frames, and three shafts disposed between the side frames in such a manner as to extend from one side frame to the other. The stopper piece is axially and pivotably supported between the side frames. The stopper piece is provided with a retaining projection which has a sloped surface for cooperating with a correspondingly sloped surface of a winding shaft, which is one of the aforenoted three shafts, in order to frictionally engage and entrap a belt portion therebetween thereby securing the belt portion within the buckle.