Optical flashes on the surface of Jupiter were observed by amateur astronomers in June and August 2010.Especially latter case was observed by four amateur astronomers in Japan.The duration of the flash was about two seconds, and the brightness was 6.2 magnitudes.This is presumed to be an equivalent or slightly smaller scale than that in June.These phenomena were bright meteors caused by the collision of small celestial bodies of a few to 10 m.If the frequency and the scale of these phenomena are investigated, the size distribution down to size of a few m can be estimated at around the giant planet region.