An air conditioning apparatus includes a case body, and an air cooling coil disposed in the case body to cool an air stream flowing thereacross. A blower is disposed in the case body, and is driven by an output shaft of a motor to blow the air stream across the air cooling coil and deliver cooled air stream forwardly and outwardly of the case body. A drain pane is disposed under the air cooling coil to collect droplets of condensate, and has a first outlet to drain water therein. A water pump includes a pump body with an accommodation chamber, and an impeller received in the chamber and provided with a driven shaft. The driven shaft extends outwardly of the pump body to form a coupling end to be coupled with the output shaft so as to enable the motor to drive the impeller to rotate. The pump body has a second inlet in fluid communication with the first outlet of the drain pane, and a second outlet so that rotation of the impeller will generate a suction force to drain the water from the first outlet via the second inlet and out of the second outlet.