An embodiment all solid state battery includes a sulfide-based solid electrolyte layer, a negative electrode comprising a negative active material layer stacked on a first surface of the solid electrolyte layer and a negative buffer layer stacked on a first surface of the negative active material layer, and a positive electrode comprising a positive active material layer stacked on a second surface of the solid electrolyte layer and a positive buffer layer stacked on a second surface of the positive active material layer.