Provided is a lithium secondary battery including a positive electrode layer composed of a lithium complex oxide sintered body, a negative electrode layer composed of a titanium-containing sintered body, a ceramic separator interposed between the positive electrode layer and the negative electrode layer, an electrolyte with which at least the ceramic separator is impregnated, and an exterior body comprising a closed space, the closed space accommodating the positive electrode layer, the negative electrode layer, the ceramic separator, and the electrolyte. The positive electrode layer, the ceramic separator, and the negative electrode layer form one integrated sintered plate as a whole, whereby the positive electrode layer, the ceramic separator, and the negative electrode layer are bonded together.