The present invention provides a cylindrical lithium-ion secondary battery. The lithium-ion battery of the present invention has a structure in which the value of B/A is optimized, where the distance between an electrode pole to which strip-form lead pieces are welded, the lead pieces being formed intermittently in the winding direction, which is the longitudinal direction of the belt-like electrodes, and the inner wall of the battery can is represented by A, and the distance between the electrode pole and the wound electrode group is represented by B, in order to secure an exhaust passage for the gas generated upon occurrence of an abnormality in the battery.