PROBLEM TO BE SOLVED: To provide a medical image processor automatically determining at least one of a shape and a size of an edition tool.SOLUTION: A medical image processor 1 includes: a storage part 11 storing a plurality of edition tools having different shapes and volume data an extraction part 13 extracting a region of an edition target from the volume data an image generation part 21 generating a medical image having the extracted region of the edition target on the basis of the extracted region of the edition target a positional relation determination part 15 determining relative positional relation between a position of the edition tool and the region of the edition target on the basis of the position of the edition tool superposed on the medical image and the extracted region of the edition target an edition tool selection part 17 selecting the edition tool used for edition of the region of the edition target from the plurality of edition tools on the basis of the determined relative positional relation and a display part 23 displaying a superposition image obtained by superposing the selected edition tool on the medical image according to the relative positional relation.
