NOVELTY - An electrochemical reaction apparatus has a porous anode (2), a porous cathode which forms a pair with porous anode, and an ion electroconductive material having ionic conductivity. The ion electroconductive material is provided between the anode and cathode. The anode and/or cathode contain metal particles-linked material (21) by which surface oxidation is carried out.    USE - Electrochemical reaction apparatus is used for ammonia decomposing element, electric power generating apparatus and gas decomposing element (all claimed) used for decomposing ammonia, nitrogen oxide and volatile organic compound e.g. xylene and toluene.    ADVANTAGE - The reduced size electrochemical reaction apparatus is economical and easy to assemble, has simple structure, high processing capacity and excellent durability, and efficiently decomposes gas.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) ammonia decomposing element, which has electrochemical reaction apparatus in which fluid containing ammonia is introduced to anode and fluid containing oxygen atom is introduced to cathode;    (2) electric power generating apparatus, which has electrochemical reaction apparatus and electric power supply components for supplying electric power to the other electric apparatuses;    (3) gas decomposing element, which has electrochemical reaction apparatus with fluid; and    (4) manufacture of electrochemical reaction apparatus, which involves forming membrane electrode assembly (MEA) of cylindrical component comprising anode as electrode (A), cathode as electrode (B) and solid oxide electrolyte (1) interposed between inner side surface of electrode (A) and outer side surface of electrode (B), providing a collector (A) having conductor wire as a collector for anode, and inserting collector (A) to inner surface side of MEA.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic structural view of anode in gas decomposing element. (Drawing includes non-English language text)    Solid oxide electrolyte (1)    Anode (2)    Metal particles-linked component (21)    Core portion of metal particles-linked component (21a)    Oxide layer (21b)    Ion-conducting ceramic (22)