It is difficult to measure a particle motion inside a dense granular flow or a fluid-particle flow because of the existence of other particles. MRI is one of the non-invasive measurement techniques for such flows. MRI can measure the velocity distribution (tagging method and phase method), which is an outstanding advantage of the MRI measurement. This paper briefly explains the principle of the MRI measurement. Then MRI is applied to some dense granular flows or fluid-particle flows, such as rotating drums, vibrated granular beds, hopper flows and spouted beds.