Provided is a folding bicycle comprising two auxiliary rear wheels at both sides of a rear wheel; a seat including a seat tube extended downward; a first crossbar having a front end pivotably connected to a lower portion of a handle above a front wheel, and a rear end fixedly connected to an intermediate portion of the seat tube; a pair of second crossbars having two front ends pivotably connected to an intermediate portion of the handle, and two rear ends fixedly connected to both ends of an hub of the rear wheel. The first crossbar passes an intermediate portion of the second crossbar and is pivotably connected thereto. A flexible shock absorbing means is provided at a joining portion of the seat tube and the second crossbars. The shock absorbing means is adapted to elastically deform when a downward force is exerted on the seat.