The present invention is an electrochemical reactor unit in which a plurality of electrochemical reactor cells constituted by a tube are housed in a porous material body having a heat releasing function and a current collecting function, these are electrically connected in series, and a fuel manifold is mounted to the connected electrochemical reactor cells; an electrochemical reactor module that comprises a plurality of the units which are arranged in fuel supply holes, and a structure supplying air directly to the entire electrochemical reactor module; and an electrochemical reaction system in which such an electrochemical reactor module is utilized.