A self-supporting type substrate for an electrochemical cell, said substrate comprising at least one electrode of the electrochemical cell having a honeycomb ceramic structure, said honeycomb ceramic structure comprising a wall portion on which a film of a solid electrolyte is to be formed. A process for producing a self-supporting type substrate for an electrochemical cell, said process comprising the steps of preparing a first body for forming a ceramic layer to constitute one of electrodes of the electrochemical cell and a second body for forming a ceramic layer to constitute an interconnector, forming a molded body by simultaneously feeding said first and second bodies into a die to form a honeycomb ceramic structure, and firing the molded body is also disclosed.