In an endoscope washer disinfector, a bath comprises a mounting plane on which an endoscope with a duct is mounted and a wall member. A connector has two ends consisting of one end located to penetrate through the wall member and to be secured watertightly to the wall member. The one end faces an opening of the duct of the endoscope mounted in the bath. The other end is connected to a fluid source storing fluid for washing and disinfecting the endoscope. A nozzle is movable in the connector along an inner passage thereof and moved toward the one end of the connector to protrude from the one end to realize a watertight and detachable connection with the opening of the duct. The fluid is supplied to the duct when the fluid is supplied from the fluid source.