Steam valve assembly

PROBLEM TO BE SOLVED: To reduce a pressure loss when opening a valve in a stem valve device.SOLUTION: A steam control valve 2 of a steam valve device 21 comprises: a casing 41 having an inlet part 43 connected to an intermediate flow passage part 30, and an outlet part 44 opened in a vertical direction, in which a flow passage 71 is formed between the inlet part 43 and the outlet part 44 and a valve seat 45 is arranged in the flow passage; a valve body 42 that can move upward and downward in the casing and is detached from and engaged with the valve seat 45 for opening and closing the flow passage 71; and a valve rod 47 that is coupled with the valve body 42, penetrates through the casing 41 on a side opposite to the outlet part 44, slides upward and downward, and is moved to the side opposite to the outlet part 44 when opening the flow passage 71. The intermediate flow passage part 30 is a circular pipe flow passage with an arc shape so that a flow of main stem flowing from an outlet part 34 of a main steam block valve 1 varies its direction from the vertical direction, and flows to the inlet part 43. The outlet part 44 is opened upward, and the valve rod 47 penetrates downward through a lower part of the casing 41.