[Object] To provide a display orientation adjustment device for a medical three-dimensional image, capable of adjusting a display orientation of a medical three-dimensional image. [Solution Means] When an observation direction changing operation is performed by a user, a control unit 1 rotatively moves the whole display image by a predetermined amount in a direction corresponding to the observation direction changing operation around a specified screen display axis. When a frontal orientation adjusting operation by rotative movement is performed, the control unit 1 rotatively moves a head image 11 by a predetermined amount in a direction corresponding to the adjusting operation around a specified reference axis (specified reference axis for rotative movement) . The control unit 1 corrects medical three-dimensional image data on a reference coordinate system on a working memory based on the specified reference axis and specified rotative movement direction and rotative movement amount.
