In a thermo-physical property measurement instrument, a light shield that shields from light except for an aperture is provided facing the front surface of a sample thin film of a sample. Heating light of repeated pulse that is output from a heating laser irradiates the sample thin film through the light shield. Temperature measurement light of continuous light that is output from a temperature measurement laser is applied to a measurement position a predetermined distance away from a heating light irradiation position on the sample thin film. A photodetector detects reflected light of the temperature measurement light off the sample thin film, and a computer acquires a thermo-reflectance signal that was digitally converted by an AD converter. The computer calculates a thermo-physical property value in the in-plane direction of the sample thin film of the sample on the basis of the acquired thermo-reflectance signal.