A sealed nonaqueous electrolyte secondary battery in which an electrode body having a positive electrode and a negative electrode that oppose each other via a separator, an electrolyte, and an additive made of an overcharge inhibitor that generates gas when a prescribed battery voltage is exceeded are housed in a battery case, this sealed nonaqueous electrolyte secondary battery including a current interrupt device that is actuated when pressure inside the battery case rises as a result of generation of the gas, wherein the positive electrode includes a positive electrode current collector and a positive electrode active material layer which is formed on the positive electrode current collector and which mainly contains a positive electrode active material, an electroconductive material layer which mainly contains an electroconductive material is provided between the positive electrode active material layer and the separator, wherein the ratio of the positive electrode active material among the entire electroconductive material layer is 5% by mass or less, the electroconductive material layer is formed on the positive electrode, and the electroconductive material layer has a porosity of 35% or higher and 55% or lower, wherein the porosity is a value calculated according to Expression below using a mass W (g) of a conductive material layer, an apparent volume V (cm 3) of the conductive material layer, and a true density p, which is a value obtained by dividing the mass W by an actual volume excluding gaps, of the conductive material layer as measured by a density measuring device according to a general constant volume dilatometric method (gas displacement pycnometry), and wherein the apparent volume is calculated as a product of an area S (cm 2) in plan view and a thickness T (cm), and the area S (cm 2) in plan view is obtained by cutting out in a square or rectangle using a punching machine or a cutter, and the thickness T is measured using a micrometer or a thickness gauge 1 − W / ρV × 100 the positive electrode includes a positive electrode current collector and a positive electrode active material layer which is formed on the positive electrode current collector and which mainly contains a positive electrode active material, an electroconductive material layer which mainly contains an electroconductive material is provided between the positive electrode active material layer and the separator, wherein the ratio of the positive electrode active material among the entire electroconductive material layer is 5% by mass or less, the electroconductive material layer is formed on the positive electrode, and the electroconductive material layer has a porosity of 35% or higher and 55% or lower, wherein the porosity is a value calculated according to Expression below using a mass W (g) of a conductive material layer, an apparent volume V (cm 3) of the conductive material layer, and a true density p, which is a value obtained by dividing the mass W by an actual volume excluding gaps, of the conductive material layer as measured by a density measuring device according to a general constant volume dilatometric method (gas displacement pycnometry), and wherein the apparent volume is calculated as a product of an area S (cm 2) in plan view and a thickness T (cm), and the area S (cm 2) in plan view is obtained by cutting out in a square or rectangle using a punching machine or a cutter, and the thickness T is measured using a micrometer or a thickness gauge 1 − W / ρV × 100