An endoscope cleaning/disinfecting apparatus comprising: a cleaning/disinfecting tank having a hollow portion, a perimeter fringe portion surrounding a perimeter of the hollow portion, and an arrangement portion where a cleaning/disinfecting target object is arrangeable, on a bottom surface of the hollow portion; a cover portion adapted to be automatically opened and closed freely relative to an opening of the cleaning/disinfecting tank; a facing portion provided on the cover portion and facing the perimeter fringe portion at a closed position where the cover portion covers the opening; an approach portion provided on an inner side with respect to the facing portion on the cover portion, the approach portion adapted to be fitted in the hollow portion at the closed position and freely coming into contact with the cleaning/disinfecting target object; a central portion provided on an inner side with respect to the approach portion on the cover portion and covering the arrangement portion at the closed position; and; an informing section adapted to give a warning; characterized by an acceleration sensor adapted to detect an acceleration change pattern when the cover portion moves from an open position to the closed position; and a control section performing automatic opening/closing control of the cover portion, and, when the acceleration change pattern detected by the acceleration sensor is different from a set pattern at the time of the cover portion moving from the open position to the closed position, judging that the approach portion comes into contact with the cleaning/disinfecting target object and performing warning control of the informing section to give a warning, wherein the distance between the approach portion and the cleaning/disinfecting tank at the time of the approach portion being fitted into the hollow portion at the closed position is less than 3.2 mm. a cleaning/disinfecting tank having a hollow portion, a perimeter fringe portion surrounding a perimeter of the hollow portion, and an arrangement portion where a cleaning/disinfecting target object is arrangeable, on a bottom surface of the hollow portion; a cover portion adapted to be automatically opened and closed freely relative to an opening of the cleaning/disinfecting tank; a facing portion provided on the cover portion and facing the perimeter fringe portion at a closed position where the cover portion covers the opening; an approach portion provided on an inner side with respect to the facing portion on the cover portion, the approach portion adapted to be fitted in the hollow portion at the closed position and freely coming into contact with the cleaning/disinfecting target object; a central portion provided on an inner side with respect to the approach portion on the cover portion and covering the arrangement portion at the closed position; and; an informing section adapted to give a warning; characterized by an acceleration sensor adapted to detect an acceleration change pattern when the cover portion moves from an open position to the closed position; and a control section performing automatic opening/closing control of the cover portion, and, when the acceleration change pattern detected by the acceleration sensor is different from a set pattern at the time of the cover portion moving from the open position to the closed position, judging that the approach portion comes into contact with the cleaning/disinfecting target object and performing warning control of the informing section to give a warning, wherein the distance between the approach portion and the cleaning/disinfecting tank at the time of the approach portion being fitted into the hollow portion at the closed position is less than 3.2 mm.