An area partitioning method for partitioning an image into a foreground and a background, the method comprising the following steps: a foreground designation step in which a computer causes a user to designate a part of pixels in an area of the image that should be the foreground in the image as a foreground designating pixel; an estimation step in which the computer estimates a foreground color distribution and a background color distribution based on a color of the foreground designating pixel designated by the user, wherein the estimation step comprises: a step of mapping a color of each pixel of the image in a predetermined color space; a step of dividing a color distribution of the image mapped in the predetermined color space into a plurality of clusters; a step of counting the foreground designating pixels included in each cluster to obtain a count result for each cluster, and of calculating, for each cluster, a score expressing the magnitude of the relationship with the foreground designating pixel based on the count result; and a step (S47, S48) of selecting at least one cluster having a large relationship with the foreground designating pixel in the plurality of clusters as the estimated foreground color distribution, and of selecting at least one cluster having a small relationship with the foreground designating pixel as the estimated background color distribution, said at least one cluster having said large relationship having a higher score than the score of said at least one cluster having said small relationship; and an area partition step in which the computer partitions the image into a foreground area and a background area with the estimated foreground color distribution and the estimated background color distribution as an initial condition. a foreground designation step in which a computer causes a user to designate a part of pixels in an area of the image that should be the foreground in the image as a foreground designating pixel; an estimation step in which the computer estimates a foreground color distribution and a background color distribution based on a color of the foreground designating pixel designated by the user, wherein the estimation step comprises: a step of mapping a color of each pixel of the image in a predetermined color space; a step of dividing a color distribution of the image mapped in the predetermined color space into a plurality of clusters; a step of counting the foreground designating pixels included in each cluster to obtain a count result for each cluster, and of calculating, for each cluster, a score expressing the magnitude of the relationship with the foreground designating pixel based on the count result; and a step (S47, S48) of selecting at least one cluster having a large relationship with the foreground designating pixel in the plurality of clusters as the estimated foreground color distribution, and of selecting at least one cluster having a small relationship with the foreground designating pixel as the estimated background color distribution, said at least one cluster having said large relationship having a higher score than the score of said at least one cluster having said small relationship; and a step of mapping a color of each pixel of the image in a predetermined color space; a step of dividing a color distribution of the image mapped in the predetermined color space into a plurality of clusters; a step of counting the foreground designating pixels included in each cluster to obtain a count result for each cluster, and of calculating, for each cluster, a score expressing the magnitude of the relationship with the foreground designating pixel based on the count result; and a step (S47, S48) of selecting at least one cluster having a large relationship with the foreground designating pixel in the plurality of clusters as the estimated foreground color distribution, and of selecting at least one cluster having a small relationship with the foreground designating pixel as the estimated background color distribution, said at least one cluster having said large relationship having a higher score than the score of said at least one cluster having said small relationship; and an area partition step in which the computer partitions the image into a foreground area and a background area with the estimated foreground color distribution and the estimated background color distribution as an initial condition.