A magnetic resonance imaging device having magnetostatic field generating means for generating a magnetostatic field in an imaging space in which an examinee is to be disposed, gradient magnetic field generating means for generating a gradient magnetic field in the imaging space, high frequency magnetic field generating means for generating a high frequency magnetic field in the imaging space, receiving means for detecting a nuclear magnetic resonance signal generated from the examinee, image creating means for creating an image by using the nuclear magnetic resonance signal detected by the receiving means, and control means for controlling the gradient and high frequency magnetic field generating means (2, 3) and the receiving means according to a predetermined pulse sequence, the predetermined pulse sequence containing an unnecessary material suppressing sequence for deleting signals from a nuclear species of unnecessary material which is not a measurement target, and a main imaging sequence, including at least one high frequency magnetic field pulse, for measuring a nuclear magnetic resonance signal used to create the image of the examinee, and wherein the unnecessary material suppressing sequence includes three or more high-frequency magnetic field CHESS pulses for selectively exciting predetermined spins in the nuclear species of the unnecessary material, wherein the magnetic resonance imaging device further comprises adjusting means adapted: for adjusting flip angles of the three or more high-frequency magnetic field CHESS pulses such that the longitudinal magnetization of the unnecessary material at the time of application of the first high-frequency magnetic field pulse of the main imaging sequence is calculated to be below a predetermined threshold in the main imaging space over a range of flip angle combinations when the application intervals between the three or more high-frequency magnetic field CHESS pulses are assumed to be fixed, and for adjusting an application interval between the last two of the three or more high-frequency magnetic field CHESS pulses or an application interval between the last one of the three or more high-frequency magnetic field CHESS pulses and the first high-frequency magnetic field pulse of the main imaging sequence with respect to the other application intervals between the three or more high-frequency magnetic field CHESS pulses, such that the longitudinal magnetization of the unnecessary material at the time of application of the first high-frequency magnetic field pulse of the main imaging sequence is calculated to be equal to a desired value for the combination of the previously adjusted flip angles; wherein the control means are adapted to apply the predetermined pulse sequence with the three or more high-fre-quency magnetic field CHESS pulses at the flip angles adjusted by the adjusting means, and the application intervals between the three or more high-frequency magnetic field CHESS pulses and the first high-frequency magnetic field pulse of the main imaging sequence as adjusted by the adjusting means. an unnecessary material suppressing sequence for deleting signals from a nuclear species of unnecessary material which is not a measurement target, and a main imaging sequence, including at least one high frequency magnetic field pulse, for measuring a nuclear magnetic resonance signal used to create the image of the examinee, and for adjusting flip angles of the three or more high-frequency magnetic field CHESS pulses such that the longitudinal magnetization of the unnecessary material at the time of application of the first high-frequency magnetic field pulse of the main imaging sequence is calculated to be below a predetermined threshold in the main imaging space over a range of flip angle combinations when the application intervals between the three or more high-frequency magnetic field CHESS pulses are assumed to be fixed, and for adjusting an application interval between the last two of the three or more high-frequency magnetic field CHESS pulses or an application interval between the last one of the three or more high-frequency magnetic field CHESS pulses and the first high-frequency magnetic field pulse of the main imaging sequence with respect to the other application intervals between the three or more high-frequency magnetic field CHESS pulses, such that the longitudinal magnetization of the unnecessary material at the time of application of the first high-frequency magnetic field pulse of the main imaging sequence is calculated to be equal to a desired value for the combination of the previously adjusted flip angles; wherein the control means are adapted to apply the predetermined pulse sequence with the three or more high-fre-quency magnetic field CHESS pulses at the flip angles adjusted by the adjusting means, and the application intervals between the three or more high-frequency magnetic field CHESS pulses and the first high-frequency magnetic field pulse of the main imaging sequence as adjusted by the adjusting means.