Provided are a vane unit and a steam turbine. A vane unit in which an outer ring and an inner ring are connected by a plurality of vanes arranged at predetermined intervals in a circumferential direction is provided with: a steam outer ring inlet portion provided in a first heating chamber of the outer ring; a steam outer ring outlet portion provided in the first heating chamber of the outer ring so as to be separated from the steam outer ring inlet portion in the circumferential direction; and a first steam passage that makes the steam outer ring inlet portion and the steam outer ring outlet portion communicate with each other in the first heating chamber of the outer ring. Thus, steam is efficiently used, and erosion due to wet steam is suppressed and a decrease in thermal efficiency is suppressed.