Sulfur isotopes are important geochemical tracers in the diverse fields of geosciences. Controlling the accuracy and precision of the microanalysis of sulfur isotopes requires well-characterized reference materials with matrices similar to those of unknown samples. This study introduces a new natural chalcopyrite reference material, TC1725, for S isotope analysis by laser ablation multiple-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). The chalcopyrite grain is homogeneous with respect to S isotopes based on a large number of measurements by LA-MC-ICP-MS and solution nebulizer (SN)-MC-ICP-MS. Isotope ratio mass spectrometry (IRMS) for S isotopic analysis produced a mean δ³⁴S_VCDT value of +12.78 ± 0.16‰ (2 s, n = 11). Results of SN-MC-ICP-MS and LA-ICP-MS analyses are consistent with the IRMS ratios within the uncertainty. A total of 981 sulfur isotope ratio spot measurements conducted on the cruciform sections and randomly selected chalcopyrite grains of TC1725 by LA-MC-ICP-MS yielded highly consistent sulfur isotope ratios.