The performance of an all-solid-state lithium-sulfur battery, comprised of a positive composite electrode with high P/S ratio (number of phosphorus atoms/number of sulfur atoms) and solid electrolyte, is investigated at 25 degrees C at several loading weights of the positive electrode. The activation energy is nearly independent of the loading weight of the positive composite electrode. This suggests that influence of the sulfur reactivity is significantly larger than those of the ionic and electric conductivities. This positive composite electrode provides a capacity of above 1550mAhg(-1) (sulfur) at 1.3mAcm(-2) and above 6600Wkg(-1) (sulfur) at 50% state-of-charge for a loading weight of 8.3mgcm(-2). Moreover, in using this positive electrode, the energy and power densities are estimated to be 520Whkg(-1) (970WhL(-1)) and 1230Wkg(-1) (2300WL(-1)), respectively, at the cell level (18650). Furthermore, the cycling performance of the cell with this composite positive electrode is excellent over severalhundred cycles.