A sintered electrode having a large cathode capacity is obtained. A method for producing a sintered electrode which uses a lithium containing composite oxide as a cathode active material, and lithium lanthanum zirconate as an oxide solid electrolyte comprises: mixing at least the lithium containing composite oxide and a hydroxide, to obtain a cathode mixture; mixing at least the lithium lanthanum zirconate and a lithium salt that has a melting point lower than the lithium lanthanum zirconate, to obtain a solid electrolyte mixture; laminating the cathode mixture and the solid electrolyte mixture, to obtain a laminate; and heating the laminate, to sinter at least the solid electrolyte mixture.