PROBLEM TO BE SOLVED: To provide a method for controlling humidity of a greenhouse for protected horticulture capable of creating environmental humidity within the greenhouse less likely to cause disease in horticultural crops grown therein while preventing leaf blight and poor growth of cultivated products.SOLUTION: A blower 11, a hot air generator 12, and a humidity sensor 21 are installed in a green house H for protected horticulture, and management divisions of relative humidity within the greenhouse are set to a low-humidity division, a medium-humidity division, and a high-humidity division, and a low humidity set value and a high humidity set value are provided as management control values of each section. When the relative humidity in the greenhouse is detected after the start of operation of the blower and the detected relative humidity is in the low humidity division below the low humidity set value, the blower is stopped for a certain period of time. When the detected relative humidity is outside the low humidity section, a heating operation is performed by the blower and a hot air generator until the relative humidity within the greenhouse decreases to the low humidity set value or less. The relative humidity in the greenhouse is detected again after stopping the blower for a fixed time, and when the re-detected relative humidity is within the medium humidity section which exceeds the low humidity set value and is less than the high humidity set value the stop time of the blower is extended for a fixed time.SELECTED DRAWING: Figure 1
