To provide a double-clamping boost vise that can clamp two workpieces concurrently and exhibits a boosted clamping effect and an automatic centering function.

The double-clamping boost vise comprises a vise body 1, a left screw rod 2, a right screw rod 3, a balancer, a gearing mechanism, a set of pushrods, and a booster mechanism. The vise body 1 has a fixed jaw 12, a left movable jaw 13 and a right movable jaw 14, and the left and right screw rods 2 and 3 are screwed into the respective bottoms of the left and right movable jaws 13 and 14. Actuation of the gearing mechanism via a handle 8 causes the left and right screw rods 2 and 3 to move the left and right movable jaws 13 and 14 toward the fixed jaw 12 until they butt against workpieces, and further application of force to the handle 8 depresses a small screw rod 62 in the gearing mechanism which in turn pushes the booster mechanism to draw the left and right screw rods 2 and 3 until the left and right movable jaws 13 and 14 grip the workpieces. With the fixed jaw 12 removed, the left and right movable jaws 13 and 14 move in their proper directions synchronously or exhibit an automatic centering function.