The present disclosure provides a cable-type secondary battery which includes: a cable-type electrode assembly comprising an inner electrode and a separation layer surrounding the outer surface of the inner electrode to prevent a short-circuit between electrodes; and a sheet-form outer electrode surrounding the outer surface of the cable-type electrode assembly, and satisfies the mathematical formula of C≥W (wherein C is the circumference of the section perpendicular to the longitudinal direction of the cable-type electrode assembly, and W is the width of the sheet-form outer electrode).