To provide a low temperature diffusion cloud chamber which is easy in temperature control and enables easy observation of a track of a particle rays, etc.

Outputs of an electronic cooling element 12 for cooling the bottom face part 11a of an observation bath 11 in which ethanol is sealed and an electric heater 15 set at an upper part of the observation bath 11 are controlled by a control device 19, thereby properly maintaining a temperature difference of the ethanol gas at the upper part and bottom part of the observation bath. A supersaturated layer A is accordingly easily obtained. When a cap for controlling a count and a direction of charged particles emitted to a charged particle source is mounted, a track of each particle can be observed more easily.