To provide the folding device for the handle post of a bicycle, which reduces the number of operations for folding and developing the handle post of a bicycle, and make the aforesaid operations simple and quick.

The lower end of the handle post 1 is provided in such a way that it can be folded afterward by means of a hinge pin 3, a locking pawl 13 which makes the switch-over of the handle post 1 between a locking condition and a lock releasing condition by means of an ous 15 that is set in the lower end part of the handle post 1 in such a way that it can be moved up and down, is supported in such a way that it can be rotatably folded behind the upper end of the handle post 1, and a lock is released or a lock is fastened by way of a rod 17 and the ous 15 while being interlocked with the folding rotation of a handle lever 5 which is locked to a developing condition by a toggle switch 7.