PROBLEM TO BE SOLVED: To provide a patient positioning technology for making it possible to, accurately, in a short time, and without exposure, perform positioning of a patient in an area irradiated with a treatment beam.SOLUTION: A patient positioning device 10 comprises: a first identification unit 12 for identifying a patient's feature point included in a surface image 11； a first calculation unit 13 for calculating first feature point coordinates P； a detection unit 14 for detecting a marker 42 from the surface image 11； a marker coordinate calculation unit 15 for calculating marker coordinates Q； a conversion parameter derivation unit 16 for deriving a conversion parameter W for performing coordinate conversion on the first feature point coordinates P to the marker coordinates Q； a second identification unit 22 for identifying the patient's feature point 43 included in a three-dimensional image 21； a third holding unit for holding position information 24 on the three-dimensional image 21； a second calculation unit 23 for calculating second feature point coordinates R on the basis of the position information 24； a conversion unit 25 for converting the second feature point coordinates R to target coordinates S by using the conversion parameter W； and a control unit 26 for controlling a projector 36 so that a pointer 44 is projected on the target coordinates S.SELECTED DRAWING: Figure 1
