In this work, we develop a unique and efficient metamaterial device known as the “hydrodynamic evener,” which can stabilize a flow field rapidly when a transition through channels with constrictions or expansions occurs. The hydrodynamic metadevice is designed from the theory of scattering cancelation for fluid flow in a porous medium. Its precise theoretical formulation furnishes it with an almost flawless capability to guarantee uniform flow, and thus we named it as the hydrodynamic evener. This hydrodynamic evener opens up new avenues for fluid manipulation and control across numerous industrial and scientific domains, including enhancing the design of microfluidic reactors and optimization of fluid flow in microfluidic devices and the structural design of various industrial equipment.