PURPOSE: To measure a saturation voltage at 100 mA or more stably, by applying a required current to a pair of probes, and measuring the characteristic of the saturation voltage with another pair of probes.

CONSTITUTION: Electrode lead-out terminals 7, 7', 8 and 8' are formed for an emitter electrode 4 and a collector electrode 6. A pair of probes 9 and 10 are contacted with the terminals 7 and 8, which are connected to the electrode 4 and the electrode 8. Another pair of probes 9' and 10' are contacted to the similar terminals 7 ' and 8'. A current is applied to the probes 9 and 10, and the characteristic of a saturation voltage is measured with the probes 9, and 10'. Then the effect of the contact resistances generated among the probes 9, 10, 9' and 10' and the terminals 7, 8, 7, and 8' is removed. Thus the saturation voltage of at 100 mA or more is measured stably.