A secondary battery includes an electrode body and an electrolytic solution, the electrode body including a positive electrode, a negative electrode, and a separator. The separator includes a resin substrate that has a multi-layer structure including a porous polyethylene layer and a porous high melting point resin layer, the porous polyethylene layer including a polyethylene resin and being disposed to face the negative electrode, and the porous high melting point resin layer including a resin having a higher melting point than the polyethylene resin. The porosity of the porous polyethylene layer is 2% to 5%. A ratio of the thickness of the porous polyethylene layer to the total thickness of the resin substrate is 0.048 to 0.091.