An endoscope reprocessor comprising: a concentration measurement chamber; a liquid concentrate supply unit configured to supply liquid concentrate containing an examination object at a first concentration to the concentration measurement chamber; a diluent supply unit configured to supply diluent for diluting the liquid concentrate to the concentration measurement chamber to prepare practical use solution containing the examination object at a second concentration; and a holding unit configured to hold a concentration sensor so that the concentration sensor is in contact with the liquid concentrate and the practical use solution, and a standard curve storage unit configured to store information on standard curve (Ls) of the concentration sensor; characterized in that the endoscope reprocessor further comprises: a standard curve production unit configured to produce information on a temporary standard curve (Lc) based on a first point at which the first concentration is associated with a sensor output value at measurement of concentration of the liquid concentrate and a second point at which the second concentration is associated with a sensor output value at measurement of concentration of the practical use solution; a calculation unit configured to calculate a deviation degree between the standard curve (Ls) and the temporary standard curve (Lc), and a determination unit configured to determine whether the temporary standard curve (Lc) is valid from the deviation degree calculated by the calculation unit. a concentration measurement chamber; a liquid concentrate supply unit configured to supply liquid concentrate containing an examination object at a first concentration to the concentration measurement chamber; a diluent supply unit configured to supply diluent for diluting the liquid concentrate to the concentration measurement chamber to prepare practical use solution containing the examination object at a second concentration; and a holding unit configured to hold a concentration sensor so that the concentration sensor is in contact with the liquid concentrate and the practical use solution, and a standard curve storage unit configured to store information on standard curve (Ls) of the concentration sensor; characterized in that the endoscope reprocessor further comprises: a standard curve production unit configured to produce information on a temporary standard curve (Lc) based on a first point at which the first concentration is associated with a sensor output value at measurement of concentration of the liquid concentrate and a second point at which the second concentration is associated with a sensor output value at measurement of concentration of the practical use solution; a calculation unit configured to calculate a deviation degree between the standard curve (Ls) and the temporary standard curve (Lc), and a determination unit configured to determine whether the temporary standard curve (Lc) is valid from the deviation degree calculated by the calculation unit. a standard curve production unit configured to produce information on a temporary standard curve (Lc) based on a first point at which the first concentration is associated with a sensor output value at measurement of concentration of the liquid concentrate and a second point at which the second concentration is associated with a sensor output value at measurement of concentration of the practical use solution; a calculation unit configured to calculate a deviation degree between the standard curve (Ls) and the temporary standard curve (Lc), and a determination unit configured to determine whether the temporary standard curve (Lc) is valid from the deviation degree calculated by the calculation unit.