A steam turbine includes a platform (100) including a front part on an upstream side of the platform, a rear part opposite the front part, and a side part extending between the front part and the rear part; a vane (200) provided on an upper surface of the platform, the vane including a leading edge facing the front part and a trailing edge extending from the front part via the side part to the rear part; and a dovetail (300) formed integrally with the platform. The dovetail slant angle (DSA) is created when the horizon is drawn at an angle formed by a dovetail center axis (DCA) of the dovetail and a rotation axis (RA), and the stagger angle (SA) corresponds to an angle formed by the leading edge and the trailing edge of the vane. The dovetail slant angle is less than the stagger angle.