The present disclosure provides a device and a method for reducing and homogenizing residual stress during machining in which a workpiece is fixed, such as milling, boring, drilling and planning, with which high-energy acoustic waves are emitted to the workpiece via a tight contact between a plurality of high-energy wave exciters on a bench and a workpiece coated with a coupling medium, and residual stress inside the machined workpiece is reduced and homogenized through elastic wave energy generated in the workpiece by the high-energy acoustic waves. In this way, the purpose of reducing and homogenizing the residual stress while machining is achieved, realizing a stress-free machining, and the deformation of the workpiece during and after machining is minimized.