1. A medical imaging apparatus comprising: a collection unit configured to collect a magnetic resonance signal from a subject by applying a uniform static magnetic field to the subject and also apply a radio-frequency magnetic field and a gradient magnetic field to the subject in accordance with a predetermined pulse sequence; a reconstruction unit configured to reconstruct a medical image concerning the subject based on the magnetic resonance signal collected by the collection unit; a first control unit configured to control the collection unit and the reconstruction unit to acquire the medical image as a positioning image that is used to set a position of a judgment region, the judgment region being a region on monitoring images for a judgment on start timing of main imaging; a notification unit configured to notify the operator of guidance information that is used to guide a region preferable as the judgment region; a setting unit configured to set the judgment region in the positioning image in accordance with specification performed by an operator; a second control unit configured to control the collection unit and the reconstruction unit providing control so as to repeatedly acquire the medical image as a monitoring image; wherein; the second control unit configured to, when the monitoring image is repeatedly acquired, control the collection unit and the reconstruction unit providing control to stop acquisition of the monitoring image and acquire the medical image as a diagnostic image; and a third control unit configured to control a display to display the monitoring images repeatedly acquired by the collection unit and the reconstruction unit and to display judgment region image representing the judgment region set by the setting unit in the monitoring image identifiably combine with the monitoring images; wherein the notification unit is configured to control the display to display an image prepared to display a setting example of the judgment region as the guidance information.