Abstract: A combination chainless driving device of a bicycle comprises a five-way seat housing a crank axle and having a connecting portion and a front connecting mount fastened to an end of a fork connecting mount fastened to an end of a fork tube and provided with a front auxiliary gear mounted thereinto. The front auxiliary gear meshes with a main gear fastened to the crank axle. Fastened to another end of the fork tube is a rear connecting mount provided with a rear main gear mount thereinto. The rear connecting mount is fastened to a gear box in a manner that the rear main gear engages a rear auxiliary gear inside the gear box. The rear auxiliary gear has a shaft portion provided with an axial hole to receive therein a rear wheel axle. The gear box has an axle locking mount provided with an axle receiving slot for locking the rear wheel axle of a nave which is provided with a drive frame covered by a semicircular frame of the gear box and fastened to the axle locking mount by means of a rear cover.