A foldable frame for bicycle is provided in the present invention. The foldable frame can be folded up in three simple steps because of the application of two releasable locking systems: (1) release a front locking system; (2) release a rear locking system;(3) fold up a pair of rear forks hinge joint with a crossbar towards the front wheel. Other parts such as seat tube and pedal bar which are hinge joint with the crossbar can be folded up towards the crossbar. To reduce weight of the frame, a single-tube suspension system is also employed at the front of the foldable frame. The foldable frame of the present invention is easy to fold, non-bulky, lightweight and affordable to strong force as compared to any conventional foldable bicycles. The present invention can be applied to bicycle or any two-wheel vehicles such as electricity-driven or petroleum-driven motorcycle.