Optical flashes on the surface of Jupiter were observed by amateur astronomers in June and August 2010. It is thought that these phenomena were bright meteors caused by the collision of small celestial bodies of a few to 10-m, and that they seemed to be more frequent than expected. If the frequency and the scale of these phenomena are investigated, the size distribution down to size of a few m can be decided at around the giant planet region. If the systematic observation is achieved, it will be a unique attempt to use the giant planets as a natural detector of small bodies.