To provide an endoscope washing/disinfecting apparatus which enables avoidance of the possibility of workers being exposed to vapor, splash of a disinfecting liquid or others during the changing work of the disinfecting liquid.

The main body of the apparatus is provided with a washing/ disinfecting system which houses an endoscope 2 in a washing tank 1 to wash and disinfect and, moreover, a connector section 38 on which a disinfecting liquid bottle 37 is mounted to supply a disinfecting liquid to a disinfecting tank 11 of the disinfecting system. In a state where the disinfecting liquid bottle 37 is connected to the connector section 38, the inside of the disinfecting liquid bottle 37 is made to communicate with the inside of the washing tank 1 of the disinfecting system to supply the disinfecting liquid to the disinfecting liquid tank 11 in the disinfecting system. After the supply of the disinfecting liquid, the disinfecting liquid bottle 37 is washed and rinsed before it is taken out.