PURPOSE: To lower the max. amplitude value of magnetic field, keeping good relation with the uniformity of magnetostatic field, by a method wherein the amplitude of gradient magnetic field is varied while the action time is also varied within a certain range.

CONSTITUTION: Differential coils α and β are arranged on both sides of the object O which is to undergo NMR tomography. The coils α and β generates gradient magnetic field G, being excited in reverse direction by a exciting driver circuit 4. Providing that the number of line pictures N required for one image is 64, and the diameter of visual field L of the gradient direction of the field G is 50cm, the first gradient field G1 is given as a pulse-like field having a half- period of sine function g(t) with 1msec period as expressed in a formula (I). The second gradient field G2 is given as the formula (II). The third gradient field G and thereafter is also given as the pulse field having a half-period of sine function, calculated on the basis of fixed formula. The gradient field number is shown as N/2, when N=64, and is 32.