To easily inject fine particles into a refrigerant passage without stopping an operation of a refrigerating device in the case that a refrigerant gradually leaks from an in-use refrigerating device.

This fine particle injection device for injecting fine particles Hm into the refrigerant passage X of the refrigerating device is composed of a first container 8 receiving the mixture of the fine particles Hm and refrigerating machine oil Lo, and a second container 9 receiving a liquid refrigerant R1 having saturation pressure higher than low pressure-side pressure in the refrigerant passage X, the first container is made to communicate with the second container 9 at an upper section, an injection pipe 11 is disposed in the first container 8 in a communicated state with a bottom of the first container 8, and connected to a service port 7 formed at a lower pressure-side pipe 5d in the refrigerating device, and the mixture of the fine particles Hm and the refrigerating machine oil Lo received in the first container 8 is injected into the refrigerant passage X through the injection pipe 11 connected to the service port 7 formed at the low pressure-side pipe 5d in the refrigerating device by the pressure of a gas refrigerant Rg evaporated from the liquid refrigerant R1 received in the second container 9.