In a steam turbine including a turbine rotor 7; a moving blade 1 secured to the turbine rotor 7; a shroud 3 provided on an outer circumferential side distal end of the moving blade 1; and an outer circumferential side stationary wall 4 internally embracing the turbine rotor 7 and forming an outer circumferential side passage wall of a steam path, the shroud 3 has an inner circumferential surface 14 so formed that a moving blade outlet flare angle α3 is greater than a moving blade inlet flare angle α2; an angle α1 formed between the outer circumferential side stationary wall 4 and the turbine central axis 50 is generally equal to the moving blade inlet flare angle α2; and an angle α4 formed between the outer circumferential side stationary wall and an turbine central axis 50 is generally equal to the moving blade outlet flare angle α3.