A bicycle crank transmission apparatus comprising: a hollow shaft member; a base plate which is coupled to the aforementioned shaft member on one side and installed securely on a bottom bracket featuring a spindle on the other side; a chainring housing which is coupled to the aforementioned shaft member in a way that allows its rotation and has a ring gear installed securely inside; a reduction gear unit arranged in the middle of the aforementioned ring gear, in which the aforementioned reduction gear unit is securely installed on the aforementioned shaft member, consists of an eccentric guide arranged in the center of the aforementioned ring gear and an eccentric gear provided to rotate along the external circumference of the aforementioned eccentric guide and having its teeth extend in one direction, and has the aforementioned ring gear engaged with the outer part of the teeth of the aforementioned eccentric gear far away from an eccentric hole of the aforementioned eccentric guide; a directly-coupled ratchet unit installed on the aforementioned ring gear which consists of multiple directly-coupled ratchets, which are installed at intervals on the external circumference of the aforementioned ring gear, extend in a radial direction, and each have operating protrusions on one side, and a directly-coupled ratchet clutch which is stacked on one side of the aforementioned ring gear, and features indentations where the aforementioned operating protrusions are received in circumferential direction, and supports that support the aforementioned operating protrusions, which are alternately formed at intervals on the internal circumference, with multiple elastic ratchets provided at intervals on the external circumference; a crank cover having the shape of a circular lid, wherein a coupling shaft is arranged in the center of the crank cover, coupled to the aforementioned spindle, and passes through a hollow of the shaft member, wherein the-clutch ratchet teeth and directly-coupled ratchet teeth are provided on an internal wall surface of the crank cover and the clutch ratchet teeth are engaged with the elastic ratchets of the aforementioned directly-coupled ratchet clutch, wherein the clutch ratchet teeth and the directly-coupled ratchet teeth are stacked on the internal wall surface of the crank cover, and wherein the directly-coupled ratchet teeth are engaged with the aforementioned directly-coupled ratchets that have extended in radial direction from the aforementioned ring gear; and a sun gear which is installed on the aforementioned coupling shaft in such a way that it only rotates in clockwise direction, when seen in a direction towards the spindle, and partially engaged with the inside of the extended teeth of the aforementioned eccentric gear, which is close to the eccentric hole of the aforementioned eccentric guide. a hollow shaft member; a base plate which is coupled to the aforementioned shaft member on one side and installed securely on a bottom bracket featuring a spindle on the other side; a chainring housing which is coupled to the aforementioned shaft member in a way that allows its rotation and has a ring gear installed securely inside; a reduction gear unit arranged in the middle of the aforementioned ring gear, in which the aforementioned reduction gear unit is securely installed on the aforementioned shaft member, consists of an eccentric guide arranged in the center of the aforementioned ring gear and an eccentric gear provided to rotate along the external circumference of the aforementioned eccentric guide and having its teeth extend in one direction, and has the aforementioned ring gear engaged with the outer part of the teeth of the aforementioned eccentric gear far away from an eccentric hole of the aforementioned eccentric guide; a directly-coupled ratchet unit installed on the aforementioned ring gear which consists of multiple directly-coupled ratchets, which are installed at intervals on the external circumference of the aforementioned ring gear, extend in a radial direction, and each have operating protrusions on one side, and a directly-coupled ratchet clutch which is stacked on one side of the aforementioned ring gear, and features indentations where the aforementioned operating protrusions are received in circumferential direction, and supports that support the aforementioned operating protrusions, which are alternately formed at intervals on the internal circumference, with multiple elastic ratchets provided at intervals on the external circumference; a crank cover having the shape of a circular lid, wherein a coupling shaft is arranged in the center of the crank cover, coupled to the aforementioned spindle, and passes through a hollow of the shaft member, wherein the-clutch ratchet teeth and directly-coupled ratchet teeth are provided on an internal wall surface of the crank cover and the clutch ratchet teeth are engaged with the elastic ratchets of the aforementioned directly-coupled ratchet clutch, wherein the clutch ratchet teeth and the directly-coupled ratchet teeth are stacked on the internal wall surface of the crank cover, and wherein the directly-coupled ratchet teeth are engaged with the aforementioned directly-coupled ratchets that have extended in radial direction from the aforementioned ring gear; and a sun gear which is installed on the aforementioned coupling shaft in such a way that it only rotates in clockwise direction, when seen in a direction towards the spindle, and partially engaged with the inside of the extended teeth of the aforementioned eccentric gear, which is close to the eccentric hole of the aforementioned eccentric guide.