Data is collected for average units including acquisition of template data and acquisition of imaging data. A frequency difference is calculated between a resonant frequency in a reference average unit and a resonant frequency of an object average unit based on phase variation of the magnetic field between the reference average unit and the object average unit. Corrected phase shift is produced in image data collected in one or more average units based on the frequency difference. An image is reconstructed based on the imaging data collected in the reference average unit and corrected imaging data concerning the object average unit constituted by one or more average units.
