1. A magnetic resonance imaging (MRI) apparatus comprising: an MRI observation-point arranging unit that arranges and defines plural operator designated observation points on a previously obtained MRI positioning image on an MRI display device, each operator designated observation point indicating a portion of an object which is to be included in a slice volume of a later performed diagnostic MRI scan; a scanning-condition receiving unit that receives data specifying (a) a number of couch position movements on which said object is placed during the later diagnostic MRI scanning and (b) a size of the slice volume which is to be imaged at each couch position; a slice-volume setting unit that sets orientation of the slice volume in order to include a maximum number of said operator designated observation points therewithin at each position to which the couch is moved, based on the previously arranged operator designated observation points and the previously received scanning conditions; and an MRI diagnostic scanning unit that subsequently scans the object at each of the multiple couch positions, based on the respectively corresponding slice volume set by the slice-volume setting unit and outputs scanned MR image data of each said slice volume at its respectively corresponding orientation and couch position.