1. A diffusion weighted image processing apparatus, comprising a dividing device configured to divide a diffusion weighted image into two or more band like regions along a direction of a gradient field pulse, and a correcting device configured to relatively correct, with mutual reference among two or more diffusion weighted images that include the diffusion weighted image and have different directions of gradient field pulses during imaging, distortions occurring in the directions of the gradient field pulses, the distortion being caused at least in part by the gradient field pulse of the diffusion weighted image and being determined in each of the two or more band like regions.