An endoscope cleaning/disinfecting apparatus comprising: a cleaning/disinfecting tank in which an endoscope is accommodated; a lid portion openable/closable relative to the cleaning/disinfecting tank; an accommodation detecting section detecting that the endoscope is accommodated in the cleaning/disinfecting tank; an opening/closing detecting section detecting an opened state and a closed state of the lid portion relative to the cleaning/disinfecting tank; a cleaning/disinfecting section for performing cleaning/disinfection of the endoscope in the cleaning/disinfecting tank; a cleaning/disinfection detecting section detecting driving of the cleaning/disinfecting section; an informing section issuing a warning; a judging section connected to the accommodation detecting section, the opening/closing detecting section and the cleaning/disinfection detecting section, the judging section detecting a first closed state, when the accommodation detection section detects that the endoscope is accommodated in the cleaning/disinfecting tank and the opening/closing detecting section detects the closed state of the lid portion and before the cleaning/disinfection detecting section detects driving of the cleaning/disinfecting section; and a control section connected to at least the opening/closing detecting section, the cleaning/disinfection detecting section, the informing section and the judging section, characterised in that the control section is configured to perform control of driving the informing section to issue a warning after the judging section has detected the first closed state and the opening/closing detecting section detects a further opened state of the lid portion before the cleaning/disinfection detecting section detects driving of the cleaning/disinfecting section. a cleaning/disinfecting tank in which an endoscope is accommodated; a lid portion openable/closable relative to the cleaning/disinfecting tank; an accommodation detecting section detecting that the endoscope is accommodated in the cleaning/disinfecting tank; an opening/closing detecting section detecting an opened state and a closed state of the lid portion relative to the cleaning/disinfecting tank; a cleaning/disinfecting section for performing cleaning/disinfection of the endoscope in the cleaning/disinfecting tank; a cleaning/disinfection detecting section detecting driving of the cleaning/disinfecting section; an informing section issuing a warning; a judging section connected to the accommodation detecting section, the opening/closing detecting section and the cleaning/disinfection detecting section, the judging section detecting a first closed state, when the accommodation detection section detects that the endoscope is accommodated in the cleaning/disinfecting tank and the opening/closing detecting section detects the closed state of the lid portion and before the cleaning/disinfection detecting section detects driving of the cleaning/disinfecting section; and a control section connected to at least the opening/closing detecting section, the cleaning/disinfection detecting section, the informing section and the judging section, characterised in that the control section is configured to perform control of driving the informing section to issue a warning after the judging section has detected the first closed state and the opening/closing detecting section detects a further opened state of the lid portion before the cleaning/disinfection detecting section detects driving of the cleaning/disinfecting section.