To provide an infrared ray monitoring device capable of detecting only a target at a short distance.

The infrared rays radiated by an object to be photographed are condensed by a lens 1 and transmit a filter 2 to form an image on an infrared ray image photographing element 3. An output signal of the infrared ray image photographing element 3 is displayed in a display device 5 as a TV video signal by electrically compensating unevenness of bias level between picture elements and unevenness of sensitivity by a video processing circuit 4. A transmitting wave length band of the filter 2 is a wave length band of 5.2 to 7.7 μm band or 14.3 to 15.7 μm band. Consequently, the infrared ray radiated by the object to be photographed at a short distance is detected well, but an infrared ray radiated by an object to be photographed at a large distance is hardly detected so that only the object to be photographed at the short distance is clearly displayed on a screen of the display device 5.