SOLID STATE BATTERY

A solid state battery that includes: a battery element body; a first external electrode on a first end surface of the battery element body; a second external electrode on a second end surface of the battery element body; and a protective layer covering a peripheral surface of the battery element body that connects the first and second end surfaces. The first external electrode covers a first end surface of the solid state battery, and the second external electrode covers a second end surface of the solid state battery. The first principal surface and the second principal surface have a pair of a first convex part and second convex part extending from the first external electrode to the second external electrode along a longitudinal direction and located at opposed end parts in a transverse direction.