A view point is set inside a hollow organ, a clip plane crossing an internal cavity of the hollow organ is set in a position spaced apart in a visual line direction from the view point, a field of view from the view point is divided into a first field-of-view range in which the inside of the hollow organ is viewed and a second field-of-view range other than the first field-of-view range, a projection image is acquired using a template which is defined so that an inner wall surface of a large intestine is able to be drawn in the first field-of-view range, a projection image is acquired using a template which is defined so that a contact surface with the inner wall surface of the air region of the large intestine is able to be drawn in the second field-of-view range, and the projection images are connected.