To provide a plating pretreatment method for a Cr and Mn-free ABS resin surface in which plating in sufficient contact with the ABS resin surface can be formed.SOLUTION: A treatment apparatus 1 has a treatment tank 2 provided with a constant-temperature heater 3 at an outer periphery, an electrolysis cell 6 connecting with piping 4 comprising a circulation pump 5, and piping 7 for supply from the electrolysis cell 6 to the treatment tank 2. The electrolysis cell 6 internally comprises an anode 6A and a cathode 6B composed of diamond electrodes, and a bipolar electrode 6C arranged between them. The treatment tank 2 and electrolysis cell 6 are filled with a sulfuric acid of a predetermined concentration, and a predetermined current is supplied from a DC power unit to the anode 6A and cathode 6B for electrolysis of the sulphuric acid, so that a sulphuric acid solution S such as a peroxodisulfuric acid can be produced and supplied to the treatment tank 2 through the piping 7.SELECTED DRAWING: Figure 1
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