An endoscope reprocessing method includes: cleaning, disinfecting, or sterilizing an inside of a pipe line and an outer surface of an endoscope accommodated in a treatment tank; rinsing the outer surface of the endoscope with a rinsing liquid while filling the inside of the pipe line of the endoscope with gas; collecting a first sample from the rinsing liquid used for rinsing the outer surface of the endoscope; rinsing the inside of the pipe line of the endoscope with the rinsing liquid; and collecting a second sample from the rinsing liquid used for rinsing the inside of the pipe line of the endoscope.