Provided is a reaction vessel for a fuel cell, and more particularly to a reaction vessel exhibiting improved thermal efficiency, and a reaction device for a steam reforming reaction for a fuel cell. The reaction device includes a cylindrical reaction catalyst chamber on which a target reaction catalyst for a predetermined target reaction is disposed; and a tubular oxidation catalyst chamber surrounding the reaction catalyst chamber, comprising an oxidation reaction catalyst therein. The reaction device according features an increased contact area between catalyst and gas, and rapidly heating of the gas in contact with the catalyst to a desired reaction temperature.