The invention belongs to the field of electrochemical mechanical polishing, and relates to a double-sided electrochemical mechanical polishing device and method for a plane component. The double-sidedelectrochemical mechanical polishing device and method for the plane component are applicable to low-stress and high-efficiency polishing of the plane component which is manufactured through a conductive material. The device comprises a double-sided grinding device, an electrochemical mechanical polishing cushion, a conductive clamping device, a power supplying part and an electrolyte supportingpart; a positive pole of a power supply and the plane component are connected through a free star shaped sheet; a negative pole of the power supply is connected to the conductive plane component through electrolytes in upper and lower cathode layers and the polishing cushion, and thus a loop is formed to realize the double-sided electrochemical mechanical polishing. The device and the method are applicable to double-sided flattening of the conductive plane component and have the advantages of being high in material removing rate, stable in circuits, smooth to drain liquid, stable to react, simple in structure, convenient to assemble, high in shaping capacity, etc.