The invention is a bicycle having adjustable orientation of the seat (6) and the pedals (4) with respect to the handle-bars (5). The bicycle comprising an x shaped frame comprised of a profile (31) and a rigid support member (32) that are rotatably connected to each other by a hollow pin (42). The rider of the bicycle can change the angle between the profile (31) and the rigid support member (32) to rotate about the hollow pin (42). The bicycle further comprises a seat (6), attached to the upper part of the rigid support member (32), a first toothed-wheel (33) attached to the frame (32) by means of a pin passing through the toothed-wheel (33) and the lower part of the rigid support member (32). The pin has a crank and pedal (4) attached to each of its ends. The bicycle also comprises a front gear and second toothed-wheel (7) attached to a pin that passes through the hollow pin (42) located between the seat (6) and the first toothed-wheel (33).