In a magnetic resonance imaging apparatus according to the present embodiment, the sequence execution control unit alternately executes an imaging sequence of collecting data for generating a diagnostic image and a navigator sequence of collecting data for generating a navigator image that is an image for motion detection. The slice position detecting unit analyzes the navigator image generated from the data collected in the navigator sequence each time the navigator sequence is executed, and thereby detects the position of a mark indicating a slice excited by the imaging sequence executed prior to the navigator sequence. The respiratory motion estimating unit estimates the motion of a portion due to the subjects respiration, based on the detected position of the mark.
