Abstract: This method for purifying chlorosilanes includes: introducing oxygen (O2) into the chlorosilanes containing a boron impurity and a phosphorous impurity in the presence of an aromatic aldehyde; treating the chlorosilanes to convert the impurities into high boiling compounds at the same time; and subjecting the chlorosilanes after having been treated to a distillation process or the like to separate the high boiling compounds of boron and phosphorous from the chlorosilanes. The high boiling compounds produced through the above described treatment are not decomposed into low boiling compounds by the heat applied after the high boiling compounds having been produced, so that the high boiling compounds can be easily separated from the chlorosilanes through treatment such as distillation. Accordingly, the boron impurity and the phosphorous impurity can be removed with a single process.