Disclosed is a cylindrical lithium secondary battery capable of improving the stability thereof against the external pressure, The cylindrical lithium secondary battery includes an electrode assembly and a core. The electrode assembly includes a first electrode sheet, a second electrode sheet and a separator interposed between the first and second electrode sheets, which are rolled together about an axis. The electrode assembly defines a space. The core has a tubular shape provided with a gap. The core includes at least one reinforcing structure extending in a direction extending along the axis. The core is inserted into the space of the electrode assembly. A housing receives the electrode assembly and core.