Abstract: A solid electrochemical element which is flexible and has improved resistance to environmental exposure includes at least one solid electrolyte sheet which is flexible, has a pair of opposing surfaces, and is comprised of solid electrolyte particles and a plastic resin, which plastic resin was coated on each particle of the solid electrolyte particles prior to formation of the at least one solid electrolyte; and at least two electrode sheets comprised of an electrode material, one of the at least two electrode sheets being provided on each of the pair of opposing surfaces of the at least one solid electrolyte sheet, wherein an ion conductive path is formed between the pair of opposing surfaces of the at least one solid electrolyte sheet by virtual contact of the solid electrolyte particles and the electrode material.