Data acquisition based on the same MRI encoding pattern is repeated at least once for each R wave occurring at time T.sub.0 used as a trigger. The necessary number of data for image reconstruction are extracted as subsets of a complete MRI data set from the resulting plural sets of acquired MRI by temporally retrospecting from the next R wave occurrence time (time T.sub.1) after the R wave (time T.sub.0) used as the trigger. The extracted data subsets are then rearranged to generate a complete composite MRI data set which is then used for image reconstruction of heart movement associated with end-diastole after the occurrence of the triggering R wave.