In order to make it possible to accurately measure the HF concentration in a BHF solution in a low concentration region using a simple structure, there are provided a relationship storage unit that stores relationships between a pH of a BHF solution and an HF concentration, a pH meter that measures the pH of the BHF solution, and a concentration calculation unit that refers to relationships stored in the relationship storage unit, and calculates the HF concentration from the pH values measured by the pH meter.
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