A foldable bicycle includes a front frame, a rear frame, two seat plates, a middle frame, a seat post, and a handlebar unit. Thus, when the bicycle is folded, the front frame, the middle frame and the rear frame are parallel with other, and the handlebar unit is folded, so that the parts of the bicycle are fully folded to reduce the volume largely, thereby greatly saving the space of storage and transportation, and thereby facilitating a user carrying the bicycle.