In a medical liquid supply device, a control unit controls a liquid supply driver so that a liquid flows from the liquid supply driver in a liquid supply path regardless of whether a liquid-supply ON mode is selected. All of the liquid flowing from the liquid supply driver flows into a communication path when the liquid-supply ON mode is not selected. At least a part of the liquid flowing from the liquid supply driver does not flow into the communication path and is thereby supplied from a distal end of the liquid supply path when the liquid-supply ON mode is selected.