The present invention relates to a hot air device for a greenhouse in a greenhouse that can control the internal humidity and a method for controlling the humidity inside a greenhouse using the hot air device. A box-shaped main body 10 having an internal installation space in order to continuously maintain the warmth inside the greenhouse by controlling the humidity inside the greenhouse by spraying water simultaneously with hot air discharge； An air suction unit 21 is provided on one side 13 of the main body 10 to open the air, and is opened in communication in the orthogonal direction of the air suction unit 21 to move air to the front side. Sirocco fan 20 provided with an air moving unit 25 to let； A coil heater 30 provided on the air discharge path on the front side of the air moving unit 25 and arranged in multiple stages, a plurality of spaced apart at regular intervals； The multi-stage arrayed coil heater 30 has a diameter of 8 to 12 mm, and the coil heater 30 has 3 of the first coil heater 31, the second coil heater 32, and the third coil heater 33. However, the sequential arrangement is made, but the separation distance w between the coil heaters 31 to 33 is 38 to 42 mm, and the coil heaters 31 to 33 have a structure of a three-phase current connecting portion 37. It is configured to be connected, and is formed on the front portion 11 of the main body 10 located on the front side of the multi-column coil heater 30 to discharge air heated through the coil heater 30 to the outside. Discharge unit 40； A spray nozzle 50 provided on the front side of the air discharge part 40 to spray water； An electric supply unit 60 and a relay unit 70 for supplying and adjusting electricity to the sirocco fan 20 and the coil heater 30； The sirocco fan 20, the coil heater 30, the spray nozzle 50, the electrical supply unit 60 and the relay unit 70 is connected to the controller 80 to control the operation； comprises a multi-stage The arranged coil heater 30 is installed in the
