An analysis device includes an acquisition unit that acquires, for a plurality of pieces of data to be analyzed having a value of each factor in a factor group, combined branch conditions obtained by combining a plurality of branch conditions in the factor group and values of the combined branch conditions of each piece of data to be analyzed of the plurality of pieces of data to be analyzed, and a search unit that divides the plurality of pieces of data to be analyzed having the values of the combined branch conditions on the basis of the combined branch conditions and searches for a first decision tree.