Enhancement of the secondary ion intensity in the TOF-SIMS spectra obtained by Au⁺ and Au₃⁺ bombardment was investigated in comparison with Ga⁺ excitation using polymer samples with different molecular weight distributions. Since the polymer samples used in this experiment have wide molecular weight distributions, the advantages of a gold cluster primary ion source over a monoatomic ion source could systematically be evaluated. It was found that a Au primary ion source for a TOF-SIMS instrument has advantages in such terms as (1) the mass effect of the monoatomic primary ion, i.e., Au⁺ vs. Ga⁺, (2) the cluster primary ion effect of Au₃⁺ compared with Au⁺ and Ga⁺, and (3)decrease in the degree of fragmentation by usage of a cluster primary ion beam compared with a monoatomic ion beam.