1. A magnetic resonance imaging device which is provided with a magnetic field generation means which respectively generates a high frequency magnetic field and a gradient magnetic field in a space where a static magnetic field is formed, a signal processing means which detects a nuclear magnetic resonance signal generated from an inspection subject placed in the space and reconstructs an image therefrom and a display means which displays the reconstructed image, wherein the signal processing means performs, by making use of at least more than one nuclear magnetic resonance signals having different times (TM) from irradiation of the high frequency magnetic field signal and generation of the nuclear magnetic resonance signals, a computation for determining phase offset distribution between the signals, an unwrap processing for correcting a principal value rotation caused in the computation and at the same time performs a judgement whether the unwrap processing is proper by making use of a parameter representing the unwrap processing state.