A manufacturing apparatus for a semiconductor device, treating a SiN film formed on a wafer with phosphoric acid solution, including a processing bath to store phosphoric acid solution provided for treatment of the wafer, a control unit for calculating integrated SiN etching amount of the phosphoric acid solution, determining necessity of quality adjustment of the phosphoric acid solution, based on correlation between the integrated SiN etching amount calculated and etching selectivity to oxide film, and calculating a quality adjustment amount of the phosphoric acid solution as needed, and also including a mechanism to adjust the quality of the phosphoric acid solution based on the quality adjustment amount calculated.