PURPOSE: To remodel the existing bicycle extremely easily into a bicycle having a prime mover at any place without remodeling the existing bicycle sharply.

CONSTITUTION: A wheel has a hub shaft 1 fixed to mutual claws of a bicycle frame so as to be mountable and demountable freely and a hub 2 by which a single collar part 13 is formed expansively in a disk shape and a rim 3 is arranged in a central part of the frame by fixing the whole spokes 16 on the tip of the collar part, and has a gear 4 fixed to the hub by being arranged concentrically with the hub shaft 1, a baseplate 5 installed between the mutual claws together with the disk shape collar part 13 by being pivoted on the hub shaft in an opposed condition to the disk shape collar part 13, an engine 6 installed on the baseplate 5 so as to drive the gear 4 by a driving gear 22 and a whirl-stop material 7 to fix the baseplate 5 to the frame.