A winding reel for optical fiber is provided with a drum and a flange. The flange is provided with first and second slits therein for receiving leading and trailing (frontward and rearward) portions of the optical fiber. The length of the slit that receives the forward end of the optical fiber extends from the outer periphery of the flange to the surface of the drum. The slit for receiving the rearward end of the optical fiber is shorter than the forward end receiving slit. The rearward end receiving slit extends from the outer periphery of the flange inwardly a distance such that the slit does not reach a position at which a maximum amount of optical fiber wound on the winding reel is located.