A porous catalyst layer containing mixed conducting oxide having substantially a perovskite structure and containing a first element selected from Co and Fe, and a second element selected from In, Sn and Y arranged in the B site in the perovskite structure is contiguous to a second surface (1a) of a selective oxygen-permeable dense continuous layer (1) containing mixed conducting oxide. A porous intermediate catalyst layer (3) containing mixed conducting oxide and at least one of Co, Fe, Mn and Pd is contiguous to a first layer (1b) of the dense continuous layer (1). A porous reactive catalyst layer (4) provided with a metal catalyst selected from at least one of Ni, Co, Ru, Rh, Pt, Pd, Ir and Re and a support is continguous to the porous intermediate catalyst layer (3) in a manner to sandwich between the dense continuous layer (1) and the porous reactive catalyst layer (4).