The invention discloses a volute spiral spring, belonging to the technical field of mechanical device design. The volute spiral spring comprises a spring coil, a fixed end, an assembly hole and a spring clamp, wherein the spring coil is formed by uniformly winding a spring sheet; the fixed end is located on the center of the spring coil; the fixed end is of a round structure; during assembly, the fixed end sleeves the gear shaft of a milling and drilling machine; the fixed end is provided with the assembly hole; a screw is adopted for penetrating through the assembly hole and fixing the fixed end on the gear shaft; the spring clamp is arranged on the left side of the outer circle of the spring coil; and during assembly, the spring clamp is inserted into a clamping groove in a spring seat hole for fixing. According to the volute spiral spring disclosed by the invention, the rigidness of the spring coil is high; elasticity is good; safety is good; the spring coil is firmly fixed on the gear shaft; and the end part of the spring clamp is designed to be arc, so that the spring clamp is inserted into the spring seat hole conveniently and smoothly.