The invention generates mass scale comparability between mass spectra which are acquired in time-of-flight mass spectrometers, particularly with ionization by matrix-assisted laser desorption. Always slightly distorted mass scales of different mass spectra from the same type of sample can be aligned. The flight times of identical ions always differ slightly from one mass spectrum to the next due to non-reproducible processes in the ionization method. Thus the apparent mass values of ion signals of identical substances in different mass spectra do not match even if the flight times are converted into mass values with the identical calibration equation. After alignment of the mass scales, mass spectra can be reliably compared with respect to deviations in intensities of bio-makers, or be added together without deterioration in the mass resolution, and improved reference spectrum libraries can be created. Furthermore, the invention allows more reliable library searches to be carried out.