Disclosed is an apparatus for and a method of mass analysis in which a presence of an accessory substance which is difficult to be analyzed can be recognized visually and clearly. The apparatus (110)for mass analysis analyzes a sample containing a substance to be measured and includes: a display unit (220); a memory unit (215) storing a theoretical peak (T) obtained by calculation with respect toa region of a mass spectrum of the substance; a matching degree calculation unit (217) calculating a matching degree from multiple peaks that each of the mass spectrum (N) of the sample in the regionand the theoretical peak have; a matching degree displaying control unit (219a) displaying the matching degree on the display unit; and a superimposition displaying control unit (219b) displaying themass spectrum of the sample and the theoretical peak in a superimposed way in a manner that is consistent with a mass-to-charge ratio.