To provide a vertical reactor having furnace tubes disposed in the vertical direction, capable of accurately instructing a boat the position of a transfer unit for transferring works stacked in a plurality of stages in the vertical direction to the boat for treating the works in the reactor.

The reactor comprises support posts 24 for horizontally holding a plurality of stages of wafers W stacked in the vertical direction of furnace tubes and each post 24 composed of a hold face 40a for holding a part of the downside of the wafer W, a non-holding face 40b and an opposite face 40c has holding grooves 40 arranged in a plurality of stages along the vertical side of the post 24. At least one of the grooves 40 is a position teaching groove 50 which is disposed at a different position from the opposite faces 40c of other grooves 40 and has an opposite face 50c as a reference plane for teaching a transfer means position data.