An apparatus for cleaning a tail gate glass for a vehicle may include a spoiler door rotatably installed on a rear spoiler; an outlet formed at a position of the rear spoiler facing the spoiler door; an air duct installed in an internal space of the rear spoiler and guiding external air introduced through the spoiler door to the outlet; a nozzle fixed to the rear spoiler and spraying a cleaning liquid to the tail gate glass; and a door opening and closing device fixed to the rear spoiler, having a first end connected to the spoiler door and a second end fluid-connected to a cleaning liquid hose, and operated to open and close the spoiler door depending on a change in a pressure of the cleaning liquid hose.