A medical liquid supply device includes a path defining portion which defines a communication path configured to allow communication between a liquid supply path and a suction path, a liquid supply unit configured to cause a liquid to flow into the liquid supply path in a flow amount greater than or equal to a standard flow amount so that the liquid supply path constantly has no parts lacking the liquid up to the communication path in a liquid supply direction, and a suction unit configured to perform suction via the suction path. The medical liquid supply device includes a control unit configured to control an amount of suction by the suction unit in accordance with a switching operation in a liquid supply mode input section to adjust a flow amount of the liquid flowing from the liquid supply path into the suction path via the communication path between a liquid-supply ON mode and a liquid-supply OFF mode.
