The axial-flow turbine includes an extraction chamber 15 disposed on the outer circumference of a turbine blade chamber 12 and an extraction opening 16. An outer diaphragm 8 forming the downstream-side wall surface of the extraction chamber 15 is provided with a projection 21 formed more radially inwardly than the downstream-side edge on the outer circumference of an adjacent bucket 2 on the upstream side of the extraction opening 16 to form the downstream-side wall surface of the extraction opening 16. The projection 21 forms an upstream-side wall surface 18 of the outer diaphragm 8 for leading a part of the working fluid to the extraction chamber 15, and an inner wall surface 19 of the outer diaphragm 8 for leading the remaining working fluid to a bucket 11 on the downstream side of the extraction opening 16.