An axial flow rotating machine includes: a rotor; a plurality of vanes; and a medium flow modification member. Each of the vanes has an inner shroud and one or more seal fins. An annular groove, which is recessed toward a radially inner side, in which the inner shroud and the seal fins are placed in a non-contact manner, is formed at a rotor shaft. A distance from an end of the inner shroud on a furthest axially downstream side to a downstream-side groove side surface is a distance (L). A distance (Lf) from a most-downstream seal fin to a medium flow modification surface is equal to or less than the distance (L) in the axially downstream side.