The vegetation index calculation device 10 collates the height distribution data indicating the distribution of the heights of the plants existing in the target region with the predicted height data of the crops for which the vegetation index is calculated, and the target region A specifying unit 11 that specifies an area in which a crop exists, and a vegetation index calculating unit 12 that calculates a vegetation index of a crop that exists in the area specified by the specifying unit 11 are provided.