Abstract: There are provided a steam valve and the like capable of preventing breakage of an auxiliary valve element and effectively suppressing the occurrence of a leak of steam in the auxiliary valve element. In the steam valve of an embodiment, the auxiliary valve element is structured to be in an open state in which the valve rod moves in an opening direction to increase a distance between an auxiliary-valve cap and a main valve element, thereby opening an auxiliary-valve steam introduction hole, and to be in a fully-closed state in which the valve rod moves in a closing direction in which the main valve element is closed to bring the auxiliary-valve cap and the main valve element into contact with each other, thereby closing the auxiliary-valve steam introduction holes.

Abstract: In a steam valve of an embodiment, a valve element of a comprises: a first valve element part positioned in the closing direction, and including a first valve element part outer peripheral surface configured to surround the valve rod; and a second valve element part positioned in the opening direction, and including a second valve element part outer peripheral surface configured to surround the valve rod. The first valve element part outer peripheral surface is a curved surface formed to have a diameter increased toward the opening direction. A diameter of boundary position between the first valve element part outer peripheral surface and the second valve element part outer peripheral surface is the same as a seat diameter of valve seat at which the valve element is brought into contact with the valve seat when the steam valve is set to a fully-closed state.