A flow guide is provided with a flange, a guide plate, and an inside member. A ring groove which is recessed to the radially outer side from an inner circumferential surface and which extends in a circumferential direction based on the axis is formed in the flange. The inside member includes a fitted portion which enters the ring groove, and a cover portion which faces the inner circumferential surface of the flange in the radial direction. The cover portion covers at least parts of the inner circumferential surface of the flange and an inner circumferential surface of the guide plate that face a tip end of a moving blade in the radial direction. The cover portion is formed from a material having a higher erosion resistance with respect to steam and steam drain than the flange.