A method of controlling the static magnetic field in an NMR spectrometer in such a way that the magnetic field can be homogenized even if there is a temperature gradient across a sample tube. A distribution of resonance frequencies and chemical shift differences within the sample tube is found by NMR measurements for each of two peaks of a calibration sample. A temperature distribution is found based on the distribution of the chemical shift differences. A distribution of chemical shifts of a solvent used for the measurements is found, based on the temperature distribution in the sample tube. Shimming is done using magnetic field gradients based on the distribution of the chemical shifts of the solvent.