An endoscopic liquid feed device to be fitted on a mouth piece of a liquid feed port which is provided on a casing of a manipulating head assembly of an endoscope in communication with an internal liquid feed passage leading to a liquid injection port at a distal end of an insertion tube of the endoscope for injecting a liquid into a body cavity. A liquid feed adaptor is detachably fitted on the mouth piece of the liquid feed port. The liquid feed adaptor is largely constituted by a Luer-Lok member having a check valve member fitted on a fore end portion thereof, a stopper ring fitted on the outer periphery of the Luer-Lok member, and a nut member rotatably fitted on the Luer-Lok member for axial displacements between the stopper ring and a flange portion provided at the outer proximal end of the Luer-Lok member. The nut member is threaded on an external screw provided on the outer periphery of the mouth piece. A Luer-Lok portion is provided within the mouth piece, and, in place of the liquid feed adaptor, a wash liquid syringe can be connected to the Luer-Lok portion of the mouth piece at the time of washing the internal liquid feed passage of the endoscope.