A buckle for a pair of band sections connected to an object at a pair of opposite positions for wearing the object on a user's body includes a frame connected to one band section, a length adjustment chain connected to the other band, a chain folding-back shaft for folding back the chain, and a folding-back shaft position adjuster for moving the position of the folding-back shaft adjustably. When the position of the shaft is changed in the length direction of the frame, the position where the chain is folded back by the shaft changes and a distance between both the band sections is adjusted.