The invention provides a dry etching method for processing a wafer having an Ru film formed on a thick Al2O3 film to be used for a magnetic head, capable of realizing high selectivity. In the etching of a wafer having disposed on an NiCr film 15 an Al2O3 film 14, an Ru film 13, an SiO2 film 12 and a resist mask 11, the Ru film 13 is etched via plasma using a processing gas containing Cl2 and O2 (FIG. 1(c)), and thereafter, the Ru film 13 is used as a mask to etch the Al2O3 film 14 via plasma using a gas mixture mainly containing BCl3 and also containing Cl2 and Ar (FIG. 1(d)).