Abstract: A thermal conductivity measuring device includes a sample holder, a light source designed to emit a pulse of light of a predetermined impulse energy, an optical system for directing the pulse of light in a light path onto the sample in the sample holder, an infrared sensor for time-dependent detection of an infrared radiation intensity emitted by the sample, and an evaluation unit designed to automatically calculate the thermal conductivity of the sample on the basis of the time-dependent infrared radiation intensity. In addition, the light source has a continuous wave laser that is designed to emit an intensity-modulated laser beam, the intensity of which is modulated with an intensity modulation frequency. The light source is arranged to emit the laser beam along a light path. The evaluation unit is designed to automatically calculate the thermal conductivity of the sample on the basis of the time-dependent infrared radiation intensity and the intensity-modulation frequency.