A steam valve control device of this embodiment controls a steam valve. The steam valve has: an upper cover in whose through hole a bush is installed; and a valve rod which is installed so as to penetrate through the through hole of the upper cover via the bush. The valve rod has a contact surface which is formed so as to come into mechanical contact with the bush when the steam valve is opened to a maximum opening degree. The steam valve control device has a control part. When a governor free operation is performed, the control part controls the steam valve by setting a limited opening degree limited to be smaller than the maximum opening degree as an upper limit. When a load limiter operation is performed, the control part controls the steam valve by setting the maximum opening degree as the upper limit.