A cleaning/disinfecting method includes a step 10 of filling a first liquid storing section with a first liquid, a step 11 of supplying, by a set amount, a second liquid to a second liquid storing section, a step 12 of moving the first liquid and the second liquid back and forth or circulating the first liquid and the second liquid between the first liquid storing section and the second liquid storing section to thereby create mixed liquid of the first liquid and the second liquid, a step 13 of detecting a ratio of the first liquid or the second liquid included in the mixed liquid, and a step 14 of comparing the ratio with a specified value to thereby check a contact degree of the mixed liquid with the first liquid storing section.
