1. A magnetic resonance imaging (MRI) apparatus comprising: a processor configured to time-serially perform undersampling on MR signals respectively received by coil channels of a radio frequency (RF) multi-coil to acquire undersampled K-t space data; and an image processor configured to acquire a time-space correlation coefficient based on noise information of the coil channels, to restore pieces of unacquired line data from the undersampled K-t space data by using the time-space correlation coefficient, to acquire restored K-t space data, and to inversely estimate acquired line data included in the undersampled K-t space data by using the restored K-t space data and the time-space correlation coefficient, wherein, when a difference between a value of the inversely estimated line data and a value of the acquired line data is greater than a threshold, the image processor repeats operations of acquiring the time-space correlation coefficient, restoring the pieces of the unacquired line data, and inversely estimating the acquired line data until the difference becomes less than or equal to the threshold.