A steam valve has a tubular stop valve configured to move toward an upper end side and a lower end side along an axial direction when the stop valve is opened and closed respectively; and a valve main body configured to accommodate the stop valve. The stop valve has a ring-shaped protrusion portion protruded outwardly in a radial direction. The valve main body has an accommodation space for accommodating the protrusion portion which is divided by the protrusion portion into a first pressure space and a second pressure space. First and second feed/discharge portions configured for adjusting a pressure in the first pressure space and the second pressure space respectively are further provided. The protrusion portion is moved upwardly and downwardly by adjusting the pressure in the first pressure space and the second pressure space.