PROBLEM TO BE SOLVED: To make it possible to automatically generate a forest phase segment map from an aerial photograph etc. with high accuracy.SOLUTION: A forest phase analyzer comprises: a statistic distribution creation unit 26; a teacher data determination unit 28; and a forest phase segment map creation unit 30. The statistic distribution creation unit 26 sets an attention region in an original image which is obtained by photographing a target region from the sky at a second period corresponding to each forest phase region of the target region including the forest in an existing forest phase segment map at a first period so that statistic distribution of characteristic information with respect to the image extracted by a prescribed element region in an attention region of each forest phase is obtained. The teacher data determination unit 28 determines, when non-change region where the forest phase is not changed from the first period in each attention region occupies the greater part of the attention re
