PURPOSE: To enable a semiconductor device with soldering failure, etc., of a semiconductor chip to be screened as a non-conforming article positively by settin a forward-voltage measurement point at a rear portion from a middle point of a period when a rectangular wave constant current is conducting.

CONSTITUTION: A rectangular wave constant current is supplied. Also, a point when a forward voltacje VF is measured is set to t02. Namely, the time t02 is set to a point which is after 1/2 of t0-t1 and before an end point t1 of a conduction time, thus enabling a diode D of a waveform 2 with a forward voltage value VF2 which is higher than a specified value VF1 to be selected as a non-conforming article. Further, a point for measuring VF can be set to a point t01 which is ahead of 1/2 point of t0-t1, where the specified forward current value is in a relationship VF1<VF2. In this manner, VF1 and VF2 are measured at both points t01 and t02 and further only a diode with a uniform characteristic can be screened by eliminating one with a higher measured forward voltage value than a specified value forward voltage value at either point.