Elimination of stacking faults in a silicon epitaxial layer of (100) orientation by heat treatment has been investigated by observing repeated etching patterns. Similar to the (111) orientation case, two types of stacking faults are observed: one is eliminated easily by heat treatment and the other is stable and cannot be eliminated. This communication describes the results of experiments and observations on the stacking faults elimination of a (100) face epitaxial layer. From the experimental results, it was found that elimination proceeds locally not only from the surface of the growth layer to the substrate, but also from partial dislocation of the stacking fault under the surface of the growth layer. Elimination at the partial dislocation is explained.