A sulfuric acid electrolyte is produced efficiently as a functional solution and persulfuric acid produced by electrolysis is supplied efficiently to a use side while suppressing self-decomposition thereof.A functional solution supply system adapted to electrolyze a sulfuric acid solution to prepare a functional solution and supply the functional solution to a use side, comprises a storage tank 2 for storing the sulfuric acid solution, an electrolyzing apparatus (electrolytic cell 3) for electrolyzing the sulfuric acid solution, heating means (heater 5) for heating the sulfuric acid solution, cooling means (cooler 4) for cooling the sulfuric acid solution, a first circulation line 11 for returning the sulfuric acid solution discharged from the storage tank 2 to the storage tank 2 through the electrolyzing apparatus without passing through the heating means, a second circulation line 12 for returning the sulfuric acid solution introduced from the use side (cleaning machine 1) to the use side through the cooling means and the storage tank 2 in this order without passing through the heating means, and a third circulation line 13 for returning the sulfuric acid solution introduced from the use side to the use side through the heating means (heater 5) without passing through the cooling means and the storage tank 2.