To provide a combination bicycle capable of completing a disassembly/assembly work of front/rear frames by a single combining device.

The combination bicycle mainly consists of a front frame and a rear frame. Combination tubes fixed to the rear frame by a rear portion of an upper tube of the front frame and a connection tube form combining devices to be connected to each other. The combination tubes fix a rear portion of the upper tube passing through a hollow tube opened in both ends by holding the rear portion by a clamp. In addition, an insertion member such as an inner recessed slot is installed in a bottom of the upper tube, and another insertion member capable of fitting the insertion member in an inner wall of the combination tube is provided to prevent the front/rear frames from being twisted.