To provide a medical image processor which permits a subject of observation to be displayed in a medical image in a prescribed size even when the position of the subject of observation changes due to a body movement.

A medical image processor includes a structure specification section, an image generation section, and a display control section. The structure specification section specifies a tubular structure of the interior of a subject of examination and a core line along the axial direction of the tubular structure on the basis of medical image data. The image generation section generates a medical image fronting on a prescribed subject of observation from a required viewpoint position in the tubular structure. The display control section displays the medical image in a display section. The image generation section specifies one viewpoint position for every timing so that the relative distance between the subject of observation and the viewpoint position is constant at time intervals, and generates a medical image from the one viewpoint position for every timing. The display control section displays a plurality of medical images generated for every timing in the display section along a time series.