An Inductively Coupled Plasma Mass Spectrometer including: a plasma ionization part; a mass analysis part; a storage part that stores ion information about mass-charge ratios and presence ratios of isotopic ions of all elements and mass-charge ratios and generation probabilities of compound ions and multivalent ions generated when the measuring object samples are plasma-ionized; a representative sample measuring part; and an element-containing inferring part that infers types of elements contained in the representative sample; an interference ion judgment part that, respective target elements in the inferred elements, judges according to ion information whether there are isotopes without interference ions; a determination part of measurement mass-charge ratio that determines the mass-charge ratio of the isotope without interference ions and a mass-charge ratio of an isotope whose a mass peak has the maximum intensity obtained by subtracting the intensity as a mass-charge ratio for measurement; and an all-sample measuring part.