A device and method of using infrared radiation to observe coal rock fracture development processes, for use in experiments to monitor coal rock fracture development using infrared radiation comprises three telescopic box bodies sleeved together. An infrared thermal imager connected to a computer is arranged at the front end of the telescopic box bodies, and a light-blocking plate is installed on a rear end. The distance between a coal rock test block and a lens of the infrared thermal imager can be freely adjusted via the three telescopic box bodies. The telescopic box bodies are installed on a rock press, and a loading test is performed on the coal rock test block.