To enable the state of an electrolytic plating solution to be analyzed with high accuracy.SOLUTION: Na kinds of measurement result data D1 from a "first measurement result" with regard to a measurement process executed in a state where a contact amount per unit time of an electrolytic plating solution X to a reference electrode 11R, a working electrode 11W and a counter electrode 11C is adjusted to a "first amount of contact" till a "Na'th measurement result" with regard to a measurement process executed in a state where the contact amount per unit time is adjusted to a "Na'th amount of contact" are acquired. The measurement result data D1 of an M'th measurement process in which a "first amount of difference" between the measurement result data D1 in an M'th measurement process in increasing order of the contact amount per unit time and the measurement result data D1 in an (M-1)'th measurement process in decreasing order of the contact amount per unit time is smaller than or equal to a predefined permissible amount of difference is specified. The state of the electrolytic plating solution X is analyzed on the basis of the measurement result data D1 of a measurement process in which the contact amount per unit time is larger than in the specified M'th measurement process.SELECTED DRAWING: Figure 1
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