Abstract: An automatic umbrella holding device on a bicycle mainly includes a clamp holder, a main supporting post, a bottom clamping frame, etc.; wherein, the said bottom clamping frame is fixedly clamped to a predetermined position on a handle bar of a bicycle; the bottom end of the main supporting post is positioned onto the said bottom clamping frame; the said clamp holder has a fixed arm and a moveable clamping arm; one end portion of the said fixed arm or the moveable clamping arm for clamping an umbrella handle grip is disposed with a clamping jacket having arcuate clamping planes for increasing the clamping effect.