To more correctly estimate a growth period of crops.SOLUTION: A growth period estimation device comprises: a normal year reference growth period setting part 11 for setting a normal year reference growth period on the basis of growth data indicating a track record of a state of growth of a crop in past several years; a counting date setting part 12 for setting a counting date of integration of a growth factor; an initial value setting part 13 for performing reverse integration of a normal year value of the growth factor on the basis of past meteorological element, to set an initial value of integration; and a present year growth period estimation part 14 for estimating a growth period of a crop in the present year, by integration of the growth factor on the basis of the meteorological element in the present year from the initial value. When the growth period of the crop is estimated by integration of the growth factor from the counting date, a proper initial value calculated by reverse integration of the normal year value of the growth factor on the basis of the past meteorological element from the normal year reference growth period, can be applied as the integration value of the growth factor on the counting date when growth of the crop has proceeded already.SELECTED DRAWING: Figure 1
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