1. A magnetic resonance imaging apparatus comprising: an imaging unit configured to acquire frames of diffusion weighted image data corresponding to different b-values by diffusion weighted imaging with applying MPG pulses corresponding to the different b-values of which application axes are same; and a strain correction unit configured to calculate a strain correction coefficient for first diffusion weighted image data based on second diffusion weighted image data to generate image data by a strain correction of the first diffusion weighted image data using the calculated strain correction coefficient, the second diffusion weighted image data being acquired while applying an MPG pulse whose polarity is opposite to the polarity of an MPG pulse used while acquiring the first diffusion weighted image data, the first diffusion weighted image data and the second diffusion weighted image data being among the frames of the diffusion weighted image data.