To provide a drain device for an automatic vending machine which can disconnect the inside of an inner box from outside air without regard to the presence and absence of drain water.

The device is provided with a rotary shaft part 49 supported rotatably in a horizontal posture so as to surround the lower part of a drain 16 formed integrally with the drain nozzle 5 part of a drain device 20 from an outer periphery, an opening/closing cover 47 extended toward one lateral side from the part 49 to be abutted directly on the drain 16 for opening and closing the drain 16 and an opening/closing body 50 consisting of a weight part 53 extended toward the other lateral side from the part 49. Since the drain 16 can be closed directly, entering of outside air can be disconnected completely between the side of a casing inside 11 and the side of a casing outside 12 without regard to the presence and absence of the drain water. Thus, heat insulation performance and thermal efficiency are improved to successively reduce power consumption required for adjusting temperature in heating or cooling.