To enable accurate remote sensing of the heat insulating characteristic of a heat insulating material by adding a simple modification to a current photo-thermal infrared detecting method.

In this method for remote-sensing the heat insulating characteristic of a heat insulating material, the periodically modified heating light 4 is radiated to a sample 1 to detect the thermal radiation light 5 emitted from the sample 1, and frequency - phase difference characteristic of the detecting signal in relation to the heating light 1 is measured, and the frequency - phase difference characteristic is analyzed to obtain the heat conductivity and temperature conductivity of the sample 1. A metal foil 2 is pushed to a surface of the heat insulating material 1 as a sample, and the heating light 4 is radiated through the metal foil 2, and while the thermal radiation light 5 is detected.