By the combined use of a decomposition vessel, chelating resin, and atomic absorption spectrometry, a simple method for the determination of copper in silicate rocks was devised. A sample was digested overnight at room temperature with small amounts of hydrofluoric acid and aqua regia in the Teflon vessel having a sealing stopper. In the presence of citrate, only the supernatant of the digested sample solution was passed through a small column of the chelating resin, Dowex A-1, at pH 4. After elution with nitric acid, copper was determined by ordinary atomic absorption spectrometry. The recovery, reproducibility, and accuracy of the method were quite satisfactory. The analytical results obtained for the standard rocks agreed well with reported results.