An apparatus for presuming positions of organs is configured to transform plural organs included in a template that is a model including the plural organs so as to match a predetermined target organ among the plural organs in the template to a corresponding organ in volume data； and perform a first processing and a second processing a predetermined number of times. The first processing includes transforming a first organ selected among the plural organs in the template according to a corresponding first organ in the volume data, and the second processing includes transforming, for each of second organs that are predetermined organs, which are influenced by transformation of the first organ, the second organ according to transformation performed for third organs that are predetermined organs, which influence the second organ in the template.
