[Object] To provide a gas decomposition apparatus and a gas decomposition method in which no safety problems occur in spite of the application of a relatively high voltage between an anode and a cathode for the purpose of decomposing odorous gases of many types.[Solution] A catalytic electrode layer 6 that contains a catalyst and is porous; a counter electrode layer 7 that forms a pair with the catalytic electrode; and an electrolyte layer 15 that is sandwiched between the catalytic electrode and the counter electrode and has ion conductivity are included. The catalyst is held by the catalytic electrode in the form of being carried by a carrier containing a conductive material or the catalyst is directly carried by the catalytic electrode. A conductive material in the catalytic electrode, the conductive material being in contact with the catalyst, is not a noncovalent carbon material.