A liquid processing apparatus includes containers 26, 27, 26a, 26b surrounding processing chambers 51, 52 for accommodating a plurality of wafers W and nozzles 54, 56 for supplying a processing liquid to the substrates W in order to perform a liquid process. The optical amplifier includes an optical amplification medium which has simultaneous inputs of a WDM signal light and a pumping light and amplifies the WDM signal light, a light source which generates the pumping light, and an amplification characteristic supervisor part which evaluates the gain tilt of amplified signal lights of different wavelengths which form the WDM signal light. Each of the arm frames is connected pivotally to a rocker via a universal connector.