High-purity trimethylaluminum has the following impurity contents: organosilicon components.ltoreq.0.5 ppm, chlorine components.ltoreq.20 ppm, hydrocarbon components.ltoreq.1,000 ppm, Ca.ltoreq.0.05 ppm, Fe.ltoreq.0.05 ppm, Mg.ltoreq.0.05 ppm, Na.ltoreq.0.05 ppm, Si (Si components other than the organosilicon components).ltoreq.0.07 ppm, Zn.ltoreq.0.05 ppm, and S.ltoreq.0.05 ppm. The high-purity trimethylaluminum can be obtained by removing impurities from crude trimethylaluminum through distillation and evaporation.