There is provided a substrate processing method capable of etching a layer containing, at least, platinum without using a halogen gas. When etching the platinum-manganese layer on a wafer W by using a tantalum (Ta) layer 38 having a certain pattern shape, a processing gas containing, at least, a carbon monoxide gas, a hydrogen gas, and a rare gas is used, and a ratio of a gas flow rate of the hydrogen gas to a total gas flow rate of the carbon monoxide gas and the hydrogen gas is in a range of from about 50% to about 75%.