To provide the device for continuously producing a diamond fine particle (hyperfine particle) by imploding a gaseous mixture of acetylene and oxygen in a liq. as a microbubble.

This device has a mixer 8 for supplying a gaseous mixture of acetylene and oxygen, a microbubble generator 11 for discharging the gaseous mixture from the mixer 8 into the water 14 in a combustion vessel 9 as a microbubble 15 and a sound wave generator 12 for allowing the sound wave to act on the microbubble 15. Further, a water circulating pipeline 20 having a pump 16 for circulating the water 14 to the combustion vessel 9, a separator 17 for separating the fine particle from the water in the pipeline 20 and a water evaporator 19 are furnished to the device. A circulating water cooler 25 is provided to the water circulating pipeline 20.