PURPOSE: To obtain the reactive ion-beam etching device excellent in anisotropic etching by furnishing a gaseous etchant feed pipe and an exhaust pipe to a plasma chamber and further providing a nonreactive gas feed pipe to a sample chamber.

CONSTITUTION: As for the etching device 1, a gaseous etchant feed pipe 7 and an exhaust pipe 8 are provided to a plasma chamber 5, and a carrier gas feed pipe 12 is furnished to a sample chamber 10. A non-reactive gas is supplied to the chamber 10 from the feed pipe 12 to keep the chamber 5 at a negative pressure, and hence the flowing of the radical in the electrically neutral ECR plasma produced in the chamber 5 into the chamber 10 is prevented. The non- reactive gas is further introduced into the chamber 5 to exhaust 8 the radical with the non-reactive gas. Meanwhile, the etching product generated when a sample 30 is etched is exhausted from the exhaust pipe 8. Accordingly, the etching component in the chamber 10 is drawn off by an ion drawing electrode 9 to leave only an ion beam IB, and the sample 30 is anisotropically etched.