Abstract: In the optical cable in accordance with the present invention, the reversal angle &phgr; from one reverse portion to the next reverse portion in an S-Z type helical groove is at least 180 degrees; and, letting W, T, and n be the width and thickness of each optical fiber ribbon and the number of stacked sheets of optical fiber ribbons, respectively, and a and b be the width and depth of the helical groove, respectively, at least each reverse portion of the helical groove has a cross-sectional form satisfying: nT<a≦{square root over (W2+L +(nT+L )2+L )}  (1) W<b  (2) whereas the remaining portion of the helical groove has a cross-sectional form satisfying: {square root over (W2+L +(nT+L )2+L )}<min(a, b)  (3).