Disclosed is use of an all-solid-state battery as a backup power source in at least one device selected from the group consisting of a computer, a laptop computer, a portable computer, a pocket computer, a workstation, a supercomputer, computer-peripheral hardware, and a server. This all-solid-state battery comprises a positive electrode layer comprising a positive-electrode active material that is an oriented polycrystalline body composed of lithium transition metal oxide grains oriented in a given direction; a solid electrolyte layer composed of a lithium-ion conductive material; and a negative electrode layer comprising a negative-electrode active material.