The present invention provides a solid-state electrolyte battery using a cathode activating substance which functions as such in an amorphous state and has a high ionic conductivity and provides a cathode activating substance used for the same. This solid-state electrolyte battery includes a laminated body. In the laminated body, a cathode-side current collector film, cathode activating substance film, solid-state electrolyte film, anode potential formation layer and anode-side current collector film are stacked above a substrate in this order. The cathode activating substance film is made of LixMyPO4−zNz, i.e., a lithium complex oxide in an amorphous state.