A ratchet buckle, which is configured to connect a first strap and a second strap, includes a controlling device, an operating device connected to the first strap, a reel passing through the controlling device and the operating device along an axial line, the second strap wound around the reel, at least one ratchet set mounted on the reel, the reel being not rotated relative to the ratchet set, and a pawl device. When the user wants to unwind the second strap from the reel, the user moves and rotates the controlling device smoothly with only one hand thereof; therefore, it's very convenient for the user to operate. The special structure making the ratchet set unidirectionally rotatable, and it doesn't need any further structure, so that it is lighter and has lower cost.