PROBLEM TO BE SOLVED: To provide a technique that performs superimposed display by simply projecting a three-dimensional reconstructed image on a two-dimensional microscope image.SOLUTION: A medical image acquisition unit 402 acquires a reconstructed image of an area containing an operative unit. A three-dimensional coordinate acquisition unit 406 acquires a three-dimensional position coordinate of a surgical instrument. A first transformation matrix acquisition unit 404 acquires a first transformation matrix for transforming the coordinate of an image coordinate system set to the reconstructed image into the coordinate of the coordinate system which three-dimensional coordinate acquisition unit 406 uses for position coordinate measurement. A second transformation matrix acquisition unit 414 estimates a second transformation matrix to be transformed into these position coordinate on the basis of the three-dimensional position coordinate of the surgical instrument and a two-dimensional position coordinate of the surgical instrument in a two-dimensional moving image photographing an operative field. An image superimposition unit 408 uses the first transformation matrix and the second transformation matrix, and superimposes at least a portion of the reconstructed image on the two-dimensional moving image as a two-dimensional image. Here, the second transformation matrix acquisition unit 414 estimates the second transformation matrix in response to the change of a field angle or a viewing direction of the moving image.
