1. An ultrasound diagnosis apparatus, comprising: an ultrasound probe; processing circuitry configured to create a 3D ultrasound image from reflected wave data of an ultrasound wave transmitted to a subject from the ultrasound probe, when a first region of interest that is a region of interest for displaying on a display the 3D ultrasound image and a second region of interest that is a region of interest included in the first region of interest and for observing a heart valve included in the 3D ultrasound image, and a projecting direction, are received from a computer interface, create a first 2D image by performing volume rendering processing on the 3D ultrasound image in the first region of interest onto a projective plane along the projecting direction, and create a second 2D image, on which motion of the heart valve can be identified, by performing ray tracing processing on the 3D ultrasound image in the second region of interest onto the projective plane along the projecting direction with a virtual light source positioned opposite to the projecting direction, and cause the created first 2D image and the created second 2D image to be displayed in a superimposed manner on the display.