1. A magnetic resonance imaging apparatus comprising: a data collection unit that repetitively performs a tag mode of applying an RF wave to at least an upstream portion of an imaging area to label a fluid flown into the imaging area and, after a lapse of an inversion time from application of the RF wave, performing magnetic resonance data collection, while changing the inversion time; an image reconstruction unit that reconstructs a plurality of tag images corresponding to a plurality of different inversion times based on magnetic resonance data collected in the tag mode; a reference image generation unit that generates a reference image based on the plurality of the tag images; and a fluid image generation unit that generates a subtraction image between each of the tag images and the reference image as a fluid image.