3-D printing techniques have found increasingly broad applications in all facets of manufacturing, and 3-D printing parts have been used to build both prototypes and commercial products. Therefore, certain requirements of commercial products such as surface finish, strength, etc. must be met. Currently most metallic 3-D printing processes use metal powders. The powders are melted and deposited layer by layer in printing. Components made through such a process generally do not possess a completely dense structure. In general, no post processing treatment, such as forging or rolling, is performed on 3-D printing parts. Therefore, voids/porosity and cracks exist inevitably in the internal and surface structures. Such defects compromise the strength and integrity of the fabricated components, and excessive material may be needed to compensate the loss of strength, erasing the weight savings aimed by additive manufacturing. A device has been designed and built for surface treatment of 3-D printing parts, especially metallic parts. The device consists of two major components: compacting heads and actuator. The compacting heads comprise of a bundle of fine shafts or rods. The semispherical ends of the rods are placed on a 3-D printed part’s surface, and their other ends are attached to permanent magnets with their polarities alternatively arranged between neighboring rods. These rods are constrained by springs to maintain a uniform contact with the part’s surface even if it’s curved. The vibratory action of these rods is driven by the actuator which provides alternating magnetic fields to the permanent magnet ends of the rods. The vibratory frequency and amplitude are controlled and changed based on the part being treated. It works in a similar way as a concrete compactor, or shot-peening which is a commercial metallic surface treatment technique by shooting fine and hard particles onto the component to remove rusts/paints etc., and/or to create a dense surface. The vibratory impacting action of the rods may locally deform the metal surface, eliminate cracks and cavities, and create a smooth surface. The dense surface structure with compressive residual stresses produced through such a treatment improves the load-bearing capability, especially fatigue strength of the component. The device can be moved around the component surface, covering the entire surface. Using a metal 3-D printing part the device is tested to understand the effects of compacting force amplitude and frequency, and the strategy of motion of the compacting heads. These effects are examined by the hardness profile change, and microstructure of the surface.