A magnetic resonance imaging apparatus and a diffusion-weighted image acquiring method form a radial k-space through a radial sampling and acquire a diffusion-weighted image from the radial k-space, with the diffusion-weighted image acquiring including receiving an echo signal generated from the subject, and forming a k-space having a plurality of sampling lines by sampling the echo signal that is received, wherein the directions of the diffusion gradient magnetic fields applied at the time of forming the sampling lines that compose the k-space to cross each other at two adjacent sampling lines.