Abstract: Disclosed is a belt buckle including a main body having a belt end fixing means for firmly holding an end of a belt, a passage for another end of the belt to thread through, and a chamber formed behind the passage for receiving a ratchet wheel, a brake member, a push plate, a push button, and springs therein. The chamber is openably closed with a back cover. The ratchet wheel has teeth projected into the passage to press against and rotate in the same direction as the moving belt. One of the springs is positioned behind the brake member to press the latter against the ratchet wheel, so that the ratchet wheel can only rotate in one direction and therefore stops the belt from moving backward. The push button can be depressed to push the push plate backward and therefore causes the brake member to disengage from the ratchet wheel, allowing the ratchet wheel to rotate in a reverse direction to loosen the belt.