PURPOSE: To test the heat resistance of a semiconductor substrate readily, by selectively projecting light or an electron beam on a substrate element, and observing the discoloring of the electrode metal of the semiconductor element or deterioration in electric characteristics before and after the projection.

CONSTITUTION: The electric characteristics of a semiconductor element, which is probed with probes 2, are measured. Then a laser beam 3, which has suitably adjusted output power, the diameter of the beam and the like, is selectively projected on the probed semiconductor element for an appropriate time period. Thereafter, the electric characteristics of the semiconductor elements are measured through the probes 2 again. The presence or absence and the degree of discoloring of an electrode metal of the probed semiconductor element before and after the projection of the laser beam 3 are observed through a microscope. The heat resistance or the heat resisting life of the probed semiconductor element is measured and judged based on the change or deterioration in the electric characteristics or the discoloring degree of the electrode metal before and after the projection of the light beam 3.