A radiotherapy equipment control device acquires reference position information for a specific location at a reference time. Furthermore, representative point reference position information is generated from reference position information for a plurality of markers at the reference time, and relative position information up to the reference position information for the specific location is generated. Moreover, representative point position information at another time is generated from the position information for a plurality of markers in a subject at the other time, which differs from the reference time. In addition, position information for the specific location at the other time is generated from the representative point position information and the relative position information. In this case, representative point reference position information and representative position information are generated on the basis of the position information and reference position information for the plurality of markers, said information having been weighted by weighting factors.
