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With three-dimensional (3D) microelectrodes used to machine microcavities in microelectrical discharge machining (micro-EDM), the processing efficiency can be greatly improved. However, the surfaces of a laminated 3D microelectrode always have stair steps, which will be further copied to the machined surfaces of the microcavities, reducing the processed surface quality. To solve the problems, the paper proposed using layer-by-layer scanning microelectrochemical machining (micro-ECM) to eliminate the stair-stepping effect of the laminated 3D microelectrodes. First, wire electrical discharge machining (WEDM) was chosen to cut Cu foils for obtaining multilayer two-dimensional (2D) microstructures. Second, the multilayer 2D microstructures were applied to thermal diffusion bonding to form 3D microelectrode blanks. Then, the 3D microelectrode blanks were processed via layer-by-layer scanning micro-ECM to eliminate the stair steps on the surfaces. The influences of applied voltage, offset distance, and layer thickness on the elimination of the stair-stepping effect were investigated in details. Experimental results show that the stair steps on the laminated 3D microelectrode surfaces were eliminated obviously under 4.0 V applied voltage, 200 μm offset distance, and 20 μm layer thickness. Finally, the laminated 3D microelectrodes without stair steps on the surfaces were applied to micro-EDM to process microcavities. Two typical microcavities without the stair steps were obtained. [ABSTRACT FROM AUTHOR]