A transmission apparatus of the U-turn type in which the extending direction of a flexible flat cable is reversed in the middle of the cable. The apparatus comprises a planet roll located between a center barrel and an outer case. The planet roll is fitted with a planet gear which is in mesh with a sun gear fixed to the center barrel, and an internal gear fixed to the outer case. When the center barrel rotates, the planet roll revolves in the same direction as the rotating direction of the barrel, thereby guiding the U-turn portion of the cable. At the same time, the planet roll rotates around its axis in the direction opposite to the rotating direction of the center barrel, whereby a guide tape is wound on the barrel and wound off the planet roll. The guide tape serves to guide and prevent the cable from slackening, so that the potential rotational frequency of the center barrel can be made high for the cable length.