The present invention is an electrically conducting ceramic having improved electrical conductivity which comprises a perovskite-type composite oxide of a composition represented by the following formula( * See Patent for Tabular Presentation * ) PS wherein A represents at least one type of atom selected from the group consisting of Sc, Y, Nd, Yb, Er, Gd, Sm and Dy, B represents at least one type of atom selected from the group consisting of Ba, Sr and Ca, and C represents at least one type of atom selected from the group consisting of Co, Fe, Ni, Ce, Zr, Mg, Al, Sb and Cr, and x, y, z, u, v and delta are the numbers that satisfy the following formulas:( * See Patent for Tabular Presentation * ) PS ( * See Patent for Tabular Presentation * ) PS ( * See Patent for Tabular for Tabular Presentation * ) PS ( * See Patent for Tabular Presentation * ) PS ( * See Patent for Tabular Presentation * ) PS and at a temperature of 1000°C in the open air,( * See Patent for Tabular Presentation * ) PS A tubular-type fuel cell containing an electroconductive ceramic in accordance with this invention as an air electrode does not deform during operation for long period of time and yields a stabilized output and a planar type fuel cell which is free from peeling of air electrodes or does not decrease its output by the deformation of the cell.