To provide a bicycle that reduces excessive use of muscles and joints in a specific part of a user while allowing using or training muscles and joints which are hardly used.

The bicycle includes a human power input device 11 capable of bidirectionally rotational input. A load wheel unit 15 is driven by transmitting human power from an output terminal of the device 11 to an input terminal of a clutch type transmission device 13 that is capable of reverse transmission and operates in a bidirectional input and unidirectional output manner, and providing output in constant rotation direction through an output terminal of the device 13. The user is allowed to choose a direction of driving power input, and drives the wheel unit 15 by providing output in the constant rotation direction at the same or different speed ratio, when the direction of driving power input is different. When the wheel unit 15 retreats, an output terminal thereof also retreats, and when a reverse direction drive occurs, it is released through a clutch device capable of connection and release control, thereby preventing the bicycle from being locked.