For the purpose of effectively suppressing shading generated in an image due to B1 inhomogeneity, there are performed an acquiring step of acquiring magnetic resonance signals simultaneously received at a body coil and a surface coil; a filtering step of applying image-based filtering for suppressing shading due to B1 inhomogeneity to a first image according to received signals from the body coil; a calculating step of calculating a sensitivity of the surface coil based on the image-based-filtered first image and a second image according to received signals from the surface coil; and a correcting step of correcting sensitivity unevenness in the second image using the sensitivity.