A lithium secondary battery having enhanced safety, which includes an electrode group, a non-aqueous electrolyte and a battery can for housing them. The electrode group includes: a positive electrode having a strip-shaped positive electrode current collector and a material mixture layer carried thereon; a negative electrode having a strip-shaped negative electrode current collector and a material mixture layer carried thereon; a separator; and a porous heat resistant layer. The positive and negative electrodes are spirally wound with the separator and the porous heat resistant layer interposed therebetween. An outermost surface of the electrode group includes an exposed portion of either of the positive and negative electrode current collectors. The exposed portion faces an inner surface of the battery can with the separator interposed therebetween, and has opposite polarity to that of the battery can.